A grippingly topical nightmare unfolded in a television drama last week. Iran had secretly built a nuclear bomb, transforming the balance of power in the Middle East. All the United States could do was cut a deal and hope for the best as Tehran demanded a seat on the security council of the United Nations.

John Bolton snorts with derision at the scenario. But the only bit that he finds remotely funny is the prospect of Iran getting a seat on the security council; to him, long-time hawk and former American ambassador to the UN, the rest is a very real and global danger. Scientific experts and intelligence agencies are divided on when Iran might be able to build a bomb: it may be one, two, five or more years away from completion. For Bolton, this uncertainty misses the vital point.

“As we all know, intelligence estimates can be wrong in multiple directions – it may be the Iranians are farther away or it may be they are a lot closer. But you cannot base your policy on the hope of ‘just in time’ nonproliferation. You have to look at the strategic position that Iran has been pursuing for close to 20 years now, which is that they want a nuclear weapons capability, and take steps to prevent that before it happens.”

A lawyer turned diplomat, Bolton, 59, has the rumpled suit and shaggy hair of an eccentric physicist. Behind the wire-rimmed glasses, however, a Vulcan logic drives him to be one of the most fluent advocates of forceful action to stop Iran going nuclear.

First, he argues, Iran is a threat to more than the Middle East: “When you add up the record of Iran in supporting terrorism, it is clearly seeking hegemony in the region and to become a player on the world stage. But Iran and North Korea are also important, not simply because of the threats they pose themselves, but because of the risk of even greater proliferation if they are perceived as having acquired and kept nuclear weapons contrary to the efforts of the US and others.

“As the Arab states see Iran progressing towards nuclear weapons they contemplate getting nuclear weapons themselves. In the past year over a dozen Arab countries have declared to the IAEA [International Atomic Energy Agency] that they, too, want peaceful civil nuclear programmes. That’s step one [towards a bomb]. So the stakes are very high.”

What do you do about it? Bolton would prefer not to be starting from where we are today: “My preference going back several years would have been regime change.” He believes the Iranian regime is fragile: great swathes of the Iranian people, especially among the educated middle classes, are deeply unhappy with President Mahmoud Ahmadinejad and the fundamentalists. Those dissidents should have been assisted, covertly and overtly, to embrace the West and move to democracy.

The problem, says Bolton, is that the CIA has become “gun-shy”. The US has deferred to the “EU three” – Britain, France and Germany – which for four years have tried to negotiate Iran out of its nuclear weapons. They have failed: “This is a case study of why diplomacy is not cost-free. That effort at failed negotiations has given Iran more than four years to perfect the complex science and technology it needs for nuclear weapons.”

In Bolton’s view, fostering regime change cannot now be relied on to prevent Iran getting the bomb: “I think the Iranians know all they need to know to create a nuclear device. The only thing that stands in their way is resources and, given that oil is at $90 a barrel or more, resources are not a constraint.”

What options does that leave? Bolton has just published a book about his political career, beginning with Ronald Reagan’s first administration and concentrating on Bolton’s time at the UN. Although its title, Surrender is not an Option, refers to his unwillingness to compromise on political principles, it also echoes how he believes the US should approach the Iranians.

If Iran won’t voluntarily yield on its nuclear ambitions it will have to be stopped by force. Critics will cry that the smartest bombs and best laid plans have gone astray before. “There’s a lot of predictions about apocalyptic responses that I think are unrealistic,” Bolton counters. He compares the example of Israel’s recent bombing raid on a suspected nuclear facility in Syria: “Look at the reaction: no response from Syria. Silence from the Arab world. No response from Iran.

“What is Iran going to do? Is it going to support terrorism in Afghanistan, Iraq, Lebanon, the Gaza Strip – as opposed to what they are doing now? Can they afford to cut off oil exports – that is, the principal source of their national wealth? They need to sell as much as anybody else, so I don’t think that’s likely.”

A year ago Bolton thought President George W Bush would tackle the Iranian dilemma, by force if necessary, before his term ends next year. Now he believes the State Department, which he lacerates for careerist covering of backsides (along with the British Foreign Office), has hobbled the will to act. Bolton says gloomily that the threat remains and will grow worse.

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