Now britain says it will do the same. Houthi rebels forced out the u. S. Backed president last month and took over a number of government buildings. The u. S. Says the Political Uncertainty creates the risk of violence that threaten yemen wes and the diplomat yemenis and the Diplomatic Community in sanaa. The u. S. Vows to bring those responsible for the death of Kayla Mueller to justice. Isis sent proof of muellers death in a private message to her parents. It included photos one showing kayla wrapped in a burial shroud. Reporter the governor of her home state of arizona has ordered flags to be flown at half staff in her honor. But for muellers family and friends, all they can do right now is mourn the loss of a young woman devoted to helping others. Cnns anna cabrera has more from Kayla Muellers hometown. Reporter Kayla Muellers parents received word of their daughters death in a message from isis. A message that included photos that confirmed the 26yearold is dead. What is still not known is how she died. Late today, kaylas aunt remembered a caring courageous young woman. Kaylas calling was to help those suffering whether in her hometown of prescott or on the other side of the world. She has done more in her incredible 26 years than many people can ever imagine doing in their lifetime. Reporter while in captivity, mueller sent a letter to her parents which they released today. Reads in part if you could say i have suffered at all throughout this whole experience, it is noble knowing how much suffering i have put it is only in knowing how much suffering i have put you through. I will never ask you to forgive me as i do not deserve forgiveness. Had worked with humanitarian groups in india, israel and the palestinian territories. By 2013 she was already in turkey helping syrian refugee. She posted this in 2011. I reject the brutality and killing that the syrian authorities are committing again the syrian people. Reporter august 3rd 2013 mueller entered syria. She travelled with a young man believed to be a syrian and alternately described as a colleague, boyfriend, or fiance. He went there to fix the Internet Connection at a hospital. Kayla apparently joined him on a trip to a war zone off limits to americans. The two stayed overnight, but the next day returning to turkey both were grabbed on the road. Muellers family didnt hear from isis for nine months. In may, 2014 their first message proof that mueller was alive. Two millions later, a ransom demand. About 7 million or kayla would be killed. That deadline passed with no further word. In the letter to her parents, mueller talks about how isis treated her. Please know that i am in a safe location completely unharmed and healthy. Put on weight, in fact. I have been treated with the utmost respect and kindness. Isis claims mueller was killed in this building by a Jordanian Air strike. Today a white house spokesman placed the blame for her death squarely on isis. This, after all, is the organization that was holding her against her will. That means they are responsible for her safety and her well being. And they are, therefore, responsible for her death. Reporter we know the president has spoken by phone with muellers parents. He sent his condolence commended kaylas selfless work and he pledged to relentlessly pursue those who had a hand in her death. Priority one is to bring kaylas body back home so the community, her family can have closure and kayla can rest surrounding by those who love her. Anna cabrera, cnn, prescott, arizona. Such an extraordinary young lady. Such a tragic ending. Yeah. And you heard an excerpt there was Kayla Muellers letter to her family while she was in captivity. If youre interested in ded dinterested head to cnn to read more. Muellers death comes just ahead of president Barack Obamas request to congress for authorization to use military force against isis. For details on that and washingtons reaction to the aid workers death, senior White House Correspondent jim accosta reports. Reporter it was the sad confirmation of what was widely feared that american hostage Kayla Mueller, once held captive by isis is dead. The president said in a statement no matter how long it takes, the United States will find and bring to justice the terrorists who are responsible for kaylas captivity and death. An emotional arizona senator, john mccain, whose state mueller called home, choked up as he paid tribute to the fallen aid worker. She will never be forgotten. Reporter the white house rejected claims from isis that mueller was killed in last weeks air strikes that came after the terrorist group burned to death a jordanian pilot. The information we have is that theres no evidence of civilians in the target area prior to the Coalition Strike taking place. Reporter with muellers death adding pressure on the white house to strike back the president is expected to officially ask congress as soon as tomorrow to back a measure to authorize the war on isis. It would replace the more openended 2002 authorization for the war in iraq. Sources say the current proposal would be specific to the fight against isis and expire in three years. One big Sticking Point remains whether the new authorization would limit u. S. Boots on the ground. Something republicans may not accept. Im not talking about an occupying american force. Im talking about a force to supplement the Regional Forces that exist today. If you took american combat power off the table in terms of ground troops, id vote against it. Reporter a sign the administration could face an uphill climb. White house chief of staff Dennis Mcdonough roaming the halls of congress trying to whip up support. One thing the white house is ruling out is any coordination with syria over air strikes. Even though that countrys leader bashar al assad, told the bbc has government is speaking to the u. S. Through third parties. Sometimes country convey messages general message. Theres nothing tactical. There had been no coordination as it relates to military operations in syria. That was the white house spokesman speaking at the end of the report. The number of foreign fighters joining isis is on the rise. A Senior Intelligence official tells cnn they are now more than 20,000 people from 90 Different Countries fighting for the terror group in iraq and syria. That number has been rising steadily over the past few months. Up from 16,000 in november. As many as 5,000 of those fighters are from western nations. We turn to another story thats captured the attention of many people here in the u. S. And across the globe. The Nbc Television network is spending one of the suspending, i should say, one of the most popular and influential news anchors in the United States for six months without pay. This comes after nightly news host Brian Williams admitted exaggerating a story about an Iraq War Mission he was on in 2003. In a statement the chief executive at Nbc Universal says williams actions are inexcusable. However, he goes on to say that williams deserves a second chance. Cnns Brian Stelzer says williams career at nbc is, of course in jeopardy. There is no precedent for this. Many dont believe williams will ever come back to the anchor chair now that hell be going away for such a long period of time. This is a severe suspension. Im not sure nbc had any other choice. They felt they had to impose some sort of harsh penalty given all of the tall tales that had been discovered that williams had been telling over the years about an Iraq War Mission in 2003. And had also had been scrutiny about stories he reported on over the years, most notably hurricane and the aftermath of the storm. The founder and editorinchief of the rap, sharon wax did man, joins us from los angeles to talk about this. Nbc news no longer seeming to stand behind Brian Williams. Youve got the suspension for six months without pay in that memo announce by nbc news president debra turnis. Has Brian Williams credibility been damaged beyond repair now . His credibility has been badly damaged. So has the credibility of nbc news in all of this. I think its really devastate whats happened to them. The fact that they would have to take such a severe measure as a suspension. But i dont feel capable of passing judgment yet on what Brian Williams credibility is or ought to be. I think we need to wait and see what the results of the investigation that nbc is conducting are. After all, Brian Williams has a very distinguished career as a reporter as an a news anchor. And his credibility up to this point has been very well deserved. Why do you think he may have been encouraged to embellish these stories . Was he seduced by fame and entertainment outside of journalism . Can we critique the u. S. Media landscape in general in some way . First of all, im sure Brian Williams is asking himself that very question right now. Why would i do that . Because its clear that he did. At least as regards the 2003 taking rpg fire sniper fire into in rpg rocket into his helicopter that actually never happened as he was reporting in iraq. Theres a number of elements here. We have someone who is a true celebrity as well as a news anchor and a journalist. This is not the first indication of the conflict that happens when somebody who has to play the role of a journalist in a dispassionate reporter and deal with big world stories and also themselves be a celebrity. At the same time Brian Williams has a real interest in entertainment and a flair for it. I mean he does like going on the late night talk shows. He was on jon stewarts daily show a bazillion times, not the exact number but something more than a dozen times. Something like that. And he was really good on it. He has a sense of humor, and he pokes fun at himself. And hes fun to watch. But is it the Perfect Question . Is that part of the problem . Jon stewart, the news today, is that he will be stepping down from his post at the daily show after this year. You could argue that jon stewart the comedian has done more to highlight certain issues than many journalists. Isnt that kind of the changing landscape that were seeing in some ways . I will argue that. I actually i absolutely believe that and argue the bigger news in terms of news culture today is that jon stewarts stepping down and the that should take first place above williams being suspended because more people who are taste makers and influencers and young people are getting their news from jon stewart like it or not than they are from Brian Williams newscast. So that is a tremendously guideline and thoughtful tremendously influential and thoughtful and truthtelling voice that we are going to be losing from our national conversation. And i for one deeply lamb that loss. Yeah. Major changes in the u. S. Media landscape. Sharon waxman, found irand ed founder and editor of the rap. Thanks for joining us. As you heard, its the end of an era for the Comedy Central network, as well. Jon stewart says hes leaving the daily show later this year. Can you believe it . The comedian has hosted the news parody show for more than 15 years, poking fun at politicians, mocking everybody in the media. Stewart talked about his decision to step down just a few hours ago. Take a listen. Its been an absolute privilege. Its been the honor of my professional life. And i thank you for watching it. For hate watching it. Whatever reason you were tuning in for, it you get in this business with the idea that maybe you have a point of view and something to express and to receive feedback from that is the greatest feeling i can ask for, and i thank you. He also said that the show deserves a less restless host. I think he felt hed been there long enough. It was time for somebody else. He wanted time with his family. And also we saw he direction a movie out of his stage. Perhaps hell be able to pursue other interests. You cant overstate how much hes done in the world of news. Young people consuming information. He has been he knows his stuff, as well. You have to know the news information to be able to be satirical about it. And he certainly showed he was able to do that and will be missed. Very smart man, indeed. Comedy central hasnt said exactly when stewart will sign off. But it happen as soon as this summer. Some other stories to get to to bring you this hour violence escalating in Eastern Ukraine ahead of crucial peace talks. Well bring you a live report from moscow and kiev ahead. Technology gives you security. Technology gives you control and now Technology Gives you Home Security and control in a new and revolutionary way. Introducing plug protect from livewatch security, an easy to use Wireless Security system customized just for your home. Control from any smartphone, tablet, or computer and monitored by professionals 24 7. Go to livewatch. Com to get plug protect Interactive Security delivered to your door. Arm or disarm your system from anywhere. 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These crimes should be punished we demand immediate, unconditional ceasefire as well as talks closing the border withdrawal of all their foreign troop from ukrainian territory. And that comment comes on the heels of a phone call between president S Barack Obama and Vladimir Putin. Mr. Obama urged the russian president to seize the opportunity for peace. For the latest we are joined by cnns Erin Mclachlan in moscow. And Senior International correspondent Fred Pleitgen in kiev. Erin there is a lot at stake in these upcoming meetings. What is achievable and what isnt given the collapse of the september Minsk Protocol which no doubt would be weighing heavy on some of the participants in these talks . Reporter hi rosemary. Well theres still some outstanding issues that the socalled Contact Group which consists of representative from kiev separatist leaders as well as monitors are trying to resolve ahead of the normandy four. The socalled Contact Group having met last night, as well. Now on the negotiating table, according to Russian Media reports, is a broader demilitarized zone. The withdrawal of heavy weaponry from the fighting areas, as well as the establishment of some sort of a perm dialogue between don bass and kiev. Really the question remains out of any sort of achieve. If anything the talks could potentially achieve, will it in fact stick, especially considering that the separatists continue to gain ground. Rosemary . Yeah. And erin u. S. President obama hasnt yet made a decision on whether or not to provide arms to ukrainian troops in an effort of course to give diplomacy a chance. Hows that playing out in moscow along with the delay in applying more economic sanctions on russia . Is that bringing more pressure to bear on the russian president to try to work to forge a ceasefire . Is it having any impact . Reporter talk of socalled lethal defense aid to the Ukrainian Military certainly not sitting well with the russians. The head of Kremlins Security Council of quoted in Russi