The source was familiar with an assessment by Defence Secretary Leon Panetta that Israel could act this northern spring before Tehran advanced further in its nuclear program.

The Washington Post reported yesterday that Mr Panetta thought there was ``strong likelihood'' that Israel could order a strike in April, May or June, before Tehran could build a nuclear weapon and have stockpiled uranium underground where it could not be reached by Israeli weapons. Israel was said to be considering a limited strike on uranium enrichment facilities at Natanz and other targets, the Post said.

US officials said they did not believe Prime Minister Benjamin Netanyahu had made a decision yet on a possible attack, and that there was disagreement within the Israeli intelligence community about the proposal.

Israel's major allies are working hard to talk it out of the unilateral military strike on Iran's nuclear facilities, arguing forcefully that an attack ultimately would strengthen, not weaken, the rulers in Tehran. The US is leading the persuasion initiative, even though Washington largely has concluded that outside argument will have little effect on Israeli decision-making.

Iran's regime says it wants to extinguish the Jewish state, and the West accuses it of assembling the materiel and know-how to build a nuclear bomb.

Israeli Defence Minister Ehud Barak said yesterday that the world was increasingly ready to consider a military strike against Iran if economic sanctions did not persuade Tehran to give up suspect parts of its nuclear program.