By ITV News Washington Correspondent Robert Moore
I think the Americans see a perfect storm brewing in the Middle East - really a war within a war - as various Jihadi groups fight each other for relevance and supremacy.
The concern in the US for counter-terrorism groups is that either Isis or its rivals in terms of al-Qaeda affiliates might seek to gain notoriety and new followers by attacking the US home land.
I don't believe there's a specific threat the US intelligence has intercepted.
But there is alarm here that some of these groups have gained deep technical knowledge of bomb-making as well as access to European followers - those are individuals who may not need a US visa and who with relative ease could get onboard a US-bound airliner.