John Bolton, the former US ambassador to the United Nations, told Tory delegates today that efforts by the UK and the EU to negotiate with Iran had failed and that he saw no alternative to a pre-emptive strike on suspected nuclear facilities in the country.

Mr Bolton, who was addressing a fringe meeting organised by Lord (Michael) Ancram, said that the Iranian president, Mahmoud Ahmadinejad, was "pushing out" and "is not receiving adequate push-back" from the west.

"I don't think the use of military force is an attractive option, but I would tell you I don't know what the alternative is.

"Because life is about choices, I think we have to consider the use of military force. I think we have to look at a limited strike against their nuclear facilities."

He added that any strike should be followed by an attempt to remove the "source of the problem", Mr Ahmadinejad.

"If we were to strike Iran it should be accompanied by an effort at regime change ... The US once had the capability to engineer the clandestine overthrow of governments. I wish we could get it back."

The fact that intelligence about Iran's nuclear activity was partial should not be used as an excuse not to act, Mr Bolton insisted.

"Intelligence can be wrong in more than one direction." He asked how the British government would respond if terrorists exploded a nuclear device at home. "'It's only Manchester?' ... Responding after they're used is unacceptable."

Mr Bolton, now a fellow at the conservative thinktank the American Enterprise Institute and the author of a forthcoming book called Surrender is Not an Option, was applauded by delegates when he described the UN as "fundamentally irrelevant".

Defending the decision to invade Iraq, he mocked the Foreign Office's "softly softly" approach to Iran's imprisonment of 15 British sailors accused of straying into Iranian waters in April this year.

They were released after Mr Ahmadinejad announced he was making a "gift" to the British people. "They [Iran] got no response from the UK or the US. If you were the Iranian leader, what conclusion do you draw?"

Mr Bolton said he did not really want "to get into the specifics of your own internal politics here" and made no comment on David Cameron's foreign policy. But he said that Gordon Brown's performance under pressure had not been tested and he hoped that Britain would not withdraw from Iraq.

"There is too much of a view in Europe that you have passed beyond history," Mr Bolton told delegates. "That everything can be worked out by negotiation ... Democrats or Republicans, we [Americans] don't see it that way."

However, he praised the French president, Nicolas Sarkozy, and his forthright criticism of Iran in recent weeks.

Raising the spectre of George Bush's "axis of evil", Mr Bolton said that Kim Jong-il's regime in North Korea was akin to a "prison camp" and that he would "sell anything to anyone".

Those who thought North Korea would give up its nuclear capability voluntarily were wrong, he said.

The regime had made similar promises during the past decade. Only reunification between North and South Korea could resolve the problem. That could be achieved "if China were to get serious" and cut off fuel supplies to Mr Kim, but the country feared a reunited Korea.

Mr Bolton told an inquiring delegate that he was not and had never been a neoconservative: "I'm not even a Reagan conservative. I'm a [Barry] Goldwater conservative. They [neocons] have somewhat - I would say excessively - Wilsonian views about the benefits of democracy."

However, the threat to world peace did not come from neoconservatives but from the perception that "we have passed beyond history", he said.

The meeting was organised by the Global Strategy Forum, of which Lord Ancram is chairman. Earlier this month, the former Conservative deputy leader criticised the direction in which David Cameron was taking the party and for "trashing" its Thatcherite heritage.

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