A US official sought to reassure Israel this week on President Barack Obama's determination to curb Iran's disputed nuclear program, as both countries prepared for the president's first visit to Israel since taking office in 2008.
The visit by Rose Gottemoeller, acting US undersecretary of state for arms control and international security, was seen by her Israeli hosts as part of an effort to smooth the way for Obama's spring trip to the region, in which the Iranian issue will loom large.
Prime Minister Binyamin Netanyahu has set a mid-2013 "red line" for halting Iranian uranium enrichment, a process with bomb-making potential, although Tehran denies having military designs.
The prospect of unilateral strikes by Israel on its arch-enemy has rattled the Obama administration, which, loath to see a new Middle East war, prefers to pursue diplomatic alternatives for now.
But the Americans, like Israel, have not ruled out force as a last resort and have built up military assets in the Gulf that are capable, US officials say, of attacking Iranian nuclear sites at short notice.
An Israeli official who met Gottemoeller said she had "reiterated the Americans' commitment to preventing a nuclear Iran, and their worries about regional proliferation, were Iran to go nuclear".
A US Embassy spokesman declined comment on the content of Gottemoeller's meetings.
Netanyahu, in a speech Monday, said the new centrifuges Iran was installing for its uranium enrichment program could cut by a third of the time needed to create a nuclear bomb.
But on Tuesday, the Iranian Foreign Ministry spokesman was quoted by the state news agency IRNA as saying that Iran was converting some of its higher-grade enriched uranium into reactor fuel.
Such a process, diplomats believe, could slow a growth in stockpiles that could be used to make weapons, pushing back the moment when Iran crosses Israel's"red line" of having enough material for a bomb.