Bolton, interviewed by telephone from Washington, was speaking a day after the International Atomic Energy Agency announced it would send a team to Teheran, at Iran's request, to work jointly on a plan ostensibly meant to clear up suspicions about the nuclear program. Iran's chief nuclear negotiator Ali Larijani had met on Sunday with IAEA head Mohamed ElBaradei, and a day earlier with top EU foreign policy envoy Javier Solana.

Bolton, however, was witheringly critical of the ongoing diplomatic contacts with Teheran, which he said were merely playing into the hands of the regime.

"The current approach of the Europeans and the Americans is not just doomed to failure, but dangerous," he said. "Dealing with [the Iranians] just gives them what they want, which is more time...

"We have fiddled away four years, in which Europe tried to persuade Iran to give up voluntarily," he complained. "Iran in those four years mastered uranium conversion from solid to gas and now enrichment to weapons grade... We lost four years to feckless European diplomacy and our options are very limited."

Bolton said flatly that "diplomacy and sanctions have failed... [So] we have to look at: 1, overthrowing the regime and getting in a new one that won't pursue nuclear weapons; 2, a last-resort use of force."

However, he added a caution as to the viability of the first of those remaining options: While "the regime is more susceptible to overthrow from within than people think," he said, such a process "may take more time than we have."

Overall, said Bolton, it was clear that Iran had surmounted "all the technical problems of uranium enrichment," and it "may well be that we have passed the point of Iran mastering the nuclear fuel cycle." If so, it was now merely a matter of time before Iran reached a bomb-making capability - "a matter of resources and available equipment," he said - and it was solely up to Iran to set the pace.

To his dismay, however, the Bush administration was still clinging to the empty notion that the sanctions route could work, "even though [the UN's sanction] Resolutions 1737 and 1747 were full of loopholes. The US is still seeking another sanctions resolution and Solana is still pursuing diplomacy," he said bitterly.

Bolton lamented that the Bush administration today was "not the same" as a presumably more robust incarnation three years ago, because of what he said was now the State Department's overwhelming dominance of foreign policy. "The State Department has adopted the European view [on how to deal with Iran] and other voices have been sidelined," he said. Secretary of State Condoleezza Rice "is overwhelmingly predominant on foreign policy."

Asked where this left Israel, Bolton said simply: "Israel's options are as limited as those of the US, except that you are in more danger in that you are closer. I hate to say that."

Bolton, who served as undersecretary of state for arms control and international security from 2001 to 2005, before taking the ambassadorial posting to the UN from August 2005 to December 2006, said the failed handling of the Iran nuclear crisis was one of the reasons he had left the Bush administration. "I felt we were watching Europe fiddling while Rome burned," he said. "It's still fiddling."

(The full interview will appear in Friday's Post.)