Families say not enough is being done. Im wolf blitzer. Youre in the situation room. We are following two major stories tonight. Investigators make a New Discovery in the crash of flight 9525 as extraordinary new images reveal just what the recovery teams are facing in the crash site in the french alps. The closest look we have gotten so far shows crews struggling to move large pieces of wreckage and perch precariously on the mountainside. The other big story, iraq. Its now declaring a major victory over isis saying its driven the terror group out of the strategically important city of tikrit. Isis captured the city last june amid reports of horrific massacres. While isis left behind snipers and traps and explosions can still be heard. The iraqi Prime Minister today visited tikrit to put the exclamation point on its liberation. The battle took a month. Government troops were aided by iranian backed shiite militias and u. S. Air strikes and now if religious tensions dont tear the iraqi forces apart, tikrit may be the jumpingoff point for the next Iraqi Military offensive. Ill speak live this hour with senator tom cotton of the intelligence and Armed Services committee. Hes standing by. Also our correspondents and analysts theyre standing by with full coverage. Well take you inside tikrit in just a few moments. But lets begin with our pentagon correspondent barbara starr. She has the very latest. Reporter wolf when iraqi Prime Minister abadi showed up in tikrit today, it was a message to the world he was trying to send that iraqi forces have their victory, that they have entered tikrit and driven isis out. But many people here at the pentagon say not so fast. Clearly, there are several hundred isis fighters still scattered throughout the city. The iraqis still working to clear the city of them and a lot of questions, because the iraqis not able really to do this all on their own. In the last weeks, the u. S. Started air strikes that pounded those isis targets that were very well dug in. Isis defenses were very strong in the city. They were able to push them back and of course the iraqis had considerable help from those iranian backed shia militias. Right now a victory for the iraqi forces but it is just the beginning of what they are going to have to deal with if they hope to hold on to this city and move ahead. Wolf . Lots of complications there. Barbara, why is this victory in tikrit so important in the overall war against isis . Reporter well tikrit literally is on that highway to mosul. The city in the north that is the big prize, the u. S. Wants the iraqis to get their fighting force in shape to move north and take mosul, the second largest city in iraq that isis has held on to for some time. Both tikrit and mosul, though very problematic. You have to be able to hold on to the city. You have to provide security. You have to provide services to the people there. You have to drive isis out long enough and far enough away that you can really credibly say you have taken control of that city. Theres a long way to go in tikrit and mosul, it could be months before iraqi forces get there. Barbara, thanks very much. Barbara starr at the pentagon. Isis may have pulled most of its fighters out of tikrit but its still a very very dangerous place. Our Senior International correspondent arwa damon made it into the city with shots still being fired and explosions still echoing. Reporter this is the main road leading through tikrit. This is the center of the city. That building we were told had a suicide bomber and a sniper on the roof. There are still various gun shots that you do hear pockets of resistance still exist. That the governors compound. When the iraqi forces went inside one of the majors was telling us it was boobytrapped. The stairway had explosives in it and when one of their officers stepped, it detonated. Two officers were killed another three soldiers wounded inside there. If we swing around a bit more you still see smoke rising and you see plumes of smoke throughout the entire city. There were widespread concerns that when this force came through Tikrit A Sunni area it would be carrying out acts of revenge, retaliation, but that smoke we are being told is not because homes were deliberately burnt. We have not been down there to see it. But because, and you hear explosions there in the distance because they are trying to defuse all of these ieds. Its not just ieds that have been placed in the streets. Its ieds, boobytrapped buildings. There have been a few occasions when the force moving into a building has opened the door and the entire building has exploded and collapsed on top of them. Now, the Iraqi Government is saying that it has won in tikrit. It is declaring victory at this stage. But what is just as important perhaps as the military aspect of this even though there are still pockets of isis resistance is going to be what happens next. This is a very sensitive situation. Everyone very concerned about the potential for sectarian tensions to reemerge here and so the Iraqi Federal police units that were with are trying their best they say, to clear it out, secure it so that the families can return eventually but the city that theyre returning to is nothing like the one that they left. Arwa damon, cnn, tikrit iraq. After a deadline came and went diplomats gave it another day to reach a framework deal on Irans Nuclear program. Now that day has also gone and some partners in the talks, they have actually gone home. The United States and iran they are still talking but the u. S. Is warning it too will walk away if necessary. While theres talk of progress the finger pointing has already escalated. Our chief National Security correspondent jim sciutto is tracking all of this for us. Jim, is the deal dead or alive . Reporter we have just learned the French Foreign minister is on his way home he left yesterday, possibly a sign of progress that they are moving towards some sort of agreement but its not the first time we have seen ministers come and go and then come again. But as you say, there is also a testier back and forth now between the two sides. Each side blaming the other for the obstacles in the talks. Listen to how the white house and Iranian Foreign minister traded comments today. This is a unique opportunity that will not be repeated and they need to take advantage of this opportunity. If we are in a situation where we sense that the talks have stalled, then yes the United States and the International Community is prepared to walk away. Reporter this could be last minute posturing, it could be a sign of real trouble in the talks but keep this in mind as well. The best that can be expected to come out of luzon this week whether tonight or tomorrow or in the coming days is not really anything signed on paper but a general statement of goals going forward. Apparently the iranian side doesnt want to sign anything. They are firmly focused on that june 30th deadline. You know this early deadline was originally intended by the west to be a sign of irans seriousness about these negotiations that they are willing to make the big concessions. That questions still open based on what we are seeing now. Certainly is. Jim sciutto, thanks very much. Lets get some analysis of whats going on. Republican senator tom cotton of arkansas is joining us. He serves on both the intelligence and Armed Services committee. Before that he served in the u. S. Military in both iraq and afghanistan. He was a u. S. Army officer, also went into the army after graduating from harvard law school. Thanks very much, senator, for joining us. Lets say you were in charge of these negotiations with javad zarif, the Iranian Foreign minister knowing what you know. What would you say to him today . I wouldnt say anything to him today because i would have left yesterday at the deadline. I wouldnt have started these negotiations to begin with not on the terms we started them in 2013 sanctions had driven iran down to its knees. I voted in the house of representatives 18 months ago to impose new sanctions on iran with 400 other members of the congress. So we could negotiate from a position of strength not of weakness. Isnt it better to have a negotiated peaceful diplomatic deal that eliminates irans potential for having a nuclear bomb than doing it militarily launching air strikes, for example, trying to destroy their Nuclear Facilities . Yes. Of course, wolf. I like most americans support a negotiated deal. But the key word that you said there was eliminated. We have to stop iran from getting a Nuclear Weapon not just today and tomorrow but 10 and 15 years from now as well. Remember it only took north korea 12 years in from the time we reached the agreed framework to the time they detonated their first Nuclear Weapon in 2006. I dont want the world to live with those consequences in 10 or 15 years because we reached a bad deal today, negotiating from a position of weakness. Lets say the sek starecretary of state, the other members of the u. N. Security council announce tomorrow a Framework Agreement but they also say we have to finish the details by the end of june. Thats when the deadline is june 30th. And they say dont impose additional sanctions during this interim period. What will be your reaction . Well any kind of agreement based on the reports we have seen out of switzerland is going to kick the can down the road on all the major details. Unfortunately, the administrations already made very dangerous concessions. If you look just in the last week what they have conceded iran had agreed to ship all of its uranium outside of the country to russia so that wouldnt be a risk. They reneged on that agreement. Secondly we are apparently willing to allow iran to continue to enrich uranium in underground fortified military bunker. They have no reason to do so. The president has said so himself. Theres no reason that we should be continuing to grant these concessions and kicking the can down the road on these Technical Details. Its important to hear what the details are. We dont know all the details yet. Say they announce a framework detail agreement tomorrow but say the remaining Technical Details still have to be worked out. What are you going to do because i know a lot of your colleagues are already saying they want to move forward with additional sanctions during this interim period. The administration the Obama Administration says that could kill a deal. Well what i have supported in the United States senate and what Many Democrats as well as republicans have supported is future perspective sanctions. Not immediate sanctions but sanctions that would go into effect if iran walked away from the table. I also supported legislation that would require congressional review period so congress has a chance to weigh in as the American People a clear majority of the American People think they should. But im not sure they are going to get to anything thats worth calling an agreement right now and deadline vss have to mean something. You have to show that youre serious and willing to walk away from the table and then come back in a position of strength not a position of weakness. They say the real deadline is june 30th. This end of march deadline was selfimposed by the u. S. Thats why they are going another day or two or three, whatever it takes. I just want to be precise on this. What you are saying is in april or may or june before the final deadline you are willing to go ahead and impose new sanctions but they would only be implemented after, if theres a failure, say, by june 30th you wouldnt begin implementing them over the next thats what the legislation that i voted for in the Banking Committee and my Republican Senate colleague from illinois proposed. Sanctions take effect in early july if theres not a deal by june 30th. I dont think we should have gone down this path to begin with. We should have imposed new sanctions in 2013 and maintained the strength of our negotiating position which is what brought iran to the table in the first place. But we certainly should not be continuing to kick the can down the road and letting iran get Nuclear Weapons in slow motion as opposed to all at once. A lot of our viewers remember you organized that letter you and 46 of your republican colleagues wrote a letter to the iranian leadership explaining your understanding of what this deal might mean. Did you ever get a response from iran to that letter . Well javad zarif, the foreign minister negotiated with them responded promptly and in public saying that International Law would trump the United States constitution which just goes to show we needed to make the statement to irans leaders in the first place. They dont understand our constitutional system of government. They dont appreciate that while the president negotiates congress has to approve any final deal. Their response indicated that we needed to communicate to them directly in the first place and that they needed to get the message straight from us because they are not getting it in switzerland. But no one wrote you back dear senator cotton i understand we received you got no response . In the same way who was your letter specifically addressed to . It was an open letter to the leaders of iran. Wasnt addressed to the ayatollah . No, sir. It was released publicly. He made a statement publicly that demonstrated the need for our letter in the first place. You didnt get an actual response in writing . No postmark. We have a lot more to talk about, including whats going on in iraq right now. Much more coming up. Big day . Ah, the usual. Moved some new cars. Hauled a bunch of steel. Kept the supermarket shelves stocked. Made sure everyone got their latest gadgets. Whats up for the next shift . Ah, nothing much. Just keeping the lights on. laugh nice. Doing the big things that move an economy. See you tomorrow, mac. See you tomorrow, sam. Just another day at norfolk southern. Hey, girl. Is it crazy that your soccer trophy is talking to you right now . It kinda is. Its as crazy as you not rolling over your old 401k. Cue the horns. 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Concludes that iran is moving forward and developing a nuclear bomb. Do you support a preemptive strike to simply destroy Irans Nuclear capabilities . I would like to see a negotiated outcome that stops iran on all paths to getting a nuclear bomb. Is that conceivable, you think . I think it would be conceivable if we would negotiate from a position of strength. Unfortunately, i dont think iran or many of our adversaries in the region take that threat of force very seriously. I have spoken personally with ambassadors from the region who just say its not believed anymore, particularly after the president walked back his socalled red line in syria after Bashar Al Assad used chemical weapons. What we need to do is reinvigorate the threat of use of force to drive our diplomacy. Diplomacy is always stronger when backed by credible threat of use of force. You dont believe the iranians take the president s, josh earnest, ash carter the defense secretary, said yesterday the military option potentially is on the table. You dont think they take that seriously . Actions have consequences. The president drew a red line in syria, then erased it. So no i dont think iran or most other countries in the region believe the United States is willing to take military action to stop iran from getting a Nuclear Weapon. Thats one reason why we are negotiating from a position of weakness. You think they take an israeli threat seriously . I think they take it more seriously than they take the u. S. Threat. Thats a