ing borders fleeing war and isis. the risk to u.s. and european security and the stability of crucial allies in the middle east. >> lebanon and close allies of the u.s. like jordan are creaking under the strain of millions of refugees. >> reporter: the u.s. is under international pressure to take in thousands. but the risk that an isis militant could slip through remains the top concern. >> there's a lot of terrorist groups operating in that part of the world. we need to make sure that fundamentally that we protect the national security of the united states of america. any asylum seeker has to go through a thorough background check. >> reporter: the potential threat may already be in the works. the american news side buzz feed quoted a syrian operative in turkey saying he is working to sneak fighters in to europe. they are being smuggled into turkey he says, hidden among