Iran president Mahmoud Ahmadinejad claimed this week that Iran had loaded its first domestically made fuel road into a nuclear reactor. Photograph: AP
Officials in key parts of the Obama administration are increasingly convinced that sanctions will not deter Tehran from pursuing its nuclear programme, and believe that the US will be left with no option but to launch an attack on Iran or watch Israel do so.
The president has made clear in public, and in private to Israel, that he is determined to give sufficient time for recent measures, such as the financial blockade and the looming European oil embargo, to bite deeper into Iran's already battered economy before retreating from its principal strategy to pressure Tehran.
But there is a strong current of opinion within the administration – including in the Pentagon and the state department – that believes sanctions are doomed to fail, and that their principal use now is in delaying Israeli military action, as well as reassuring Europe that an attack will only come after other means have been tested.
"The White House wants to see sanctions work. This is not the Bush White House. It does not need another conflict," said an official knowledgeable on Middle East policy. "Its problem is that the guys in Tehran are behaving like sanctions don't matter, like their economy isn't collapsing, like Israel isn't going to do anything.
"Sanctions are all we've got to throw at the problem. If they fail then it's hard to see how we don't move to the 'in extremis' option."