Jack Straw yesterday used his toughest language yet to rule out any military strike against Iran, highlighting the growing divide on the issue between the Foreign Office and Downing Street.
"The reason why we're opposed to military action is because it's an infinitely worse option [than diplomacy] and there's no justification for it," the foreign secretary said
Mr Straw's intervention, in response to a report in the New Yorker that the US was studying the use of "bunker-busting" nuclear bombs to disable Iran's nuclear programme, came as it emerged that the European Union was considering a series of options to push Iran towards meeting its demands.
Such steps - listed in a confidential EU paper sent to the 25 foreign ministries - include a crackdown on credit guarantees, visa bans and a formal arms embargo.
Some of the measures are likely to be controversial within the EU - Italy alone provides €4.8bn (£3.3bn) of credit guarantees for its companies' activities within Iran - but are far less divisive than talk of military action.
While Mr Straw has repeatedly described an air strike on Iran as "inconceivable", Tony Blair, prime minister, never has.
Officials at both the Foreign Office and Downing Street privately acknowledge the difference of emphasis between the two men. Mr Blair has shown signs of exasperation with Mr Straw's cautious approach, giving rise to suggestions that the foreign secretary's focus on ruling out military action is intended to heal the breach with Labour MPs upset over the Iraq war.
The Conservative party, which believes that the threat of military action should be used to force Iran to comply, is likely to exploit the divergence between the prime minister and the foreign secretary.
Yesterday Mr Straw was still franker than before. "There is no smoking gun, there is no casus belli," he said, arguing that the west merely had well-grounded suspicions that Tehran was seeking to develop nuclear weapons capability. Iran has always argued that its nuclear programme is purely peaceful.
The foreign secretary added: "The idea of a nuclear strike on Iran is completely nuts."
The New Yorker report, by veteran investigative journalist Seymour Hersh, contends that, while the US joint chiefs of staff are strongly opposed to considering a nuclear strike on Iran, the Defense Science Board, an advisory panel for the Pentagon, has backed "the idea of using tactical nuclear weapons in such situations". The article maintains that the US is stepping up contingency plans for an air strike against Iran - as did a separate report yesterday in the Washington Post.
At present the US is seeking to build support for censuring Iran at the United Nations, as well as gathering a "coalition of concerned countries" to impose sanctions on Tehran should the Security Council prove unwilling or unable to do so.
The EU paper, drawn up by the staff of Javier Solana, the bloc's foreign policy chief, may be a step in such a direction.
"A key reason for this policy review is that Iran has taken negative steps in many areas and we have to adapt our tools accordingly," said an EU diplomat.
