OME of America’s most senior military commanders are prepared to resign if the White House orders a military strike against Iran, according to highly placed defence and intelligence sources.

Tension in the Gulf region has raised fears that an attack on Iran is becoming increasingly likely before President George Bush leaves office. The Sunday Times has learnt that up to five generals and admirals are willing to resign rather than approve what they consider would be a reckless attack.

“There are four or five generals and admirals we know of who would resign if Bush ordered an attack on Iran,” a source with close ties to British intelligence said. “There is simply no stomach for it in the Pentagon, and a lot of people question whether such an attack would be effective or even possible.”

A British defence source confirmed that there were deep misgivings inside the Pentagon about a military strike. “All the generals are perfectly clear that they don’t have the military capacity to take Iran on in any meaningful fashion. Nobody wants to do it and it would be a matter of conscience for them.

“There are enough people who feel this would be an error of judgment too far for there to be resignations.”

A generals’ revolt on such a scale would be unprecedented. “American generals usually stay and fight until they get fired,” said a Pentagon source. Robert Gates, the defence secretary, has repeatedly warned against striking Iran and is believed to represent the view of his senior commanders.

The threat of a wave of resignations coincided with a warning by Vice-President Dick Cheney that all options, including military action, remained on the table. He was responding to a comment by Tony Blair that it would not “be right to take military action against Iran”.

Iran ignored a United Nations deadline to suspend its uranium enrichment programme last week. President Mahmoud Ahmadinejad insisted that his country “will not withdraw from its nuclear stances even one single step”.

The International Atomic Energy Agency reported that Iran could soon produce enough enriched uranium for two nuclear bombs a year, although Tehran claims its programme is purely for civilian energy purposes.

Nicholas Burns, the top US negotiator, is to meet British, French, German, Chinese and Russian officials in London tomorrow to discuss additional penalties against Iran. But UN diplomats cautioned that further measures would take weeks to agree and would be mild at best.

A second US navy aircraft carrier strike group led by the USS John C Stennis arrived in the Gulf last week, doubling the US presence there. Vice Admiral Patrick Walsh, the commander of the US Fifth Fleet, warned: “The US will take military action if ships are attacked or if countries in the region are targeted or US troops come under direct attack.”

But General Peter Pace, chairman of the joint chiefs of staff, said recently there was “zero chance” of a war with Iran. He played down claims by US intelligence that the Iranian government was responsible for supplying insurgents in Iraq, forcing Bush on the defensive.

Pace’s view was backed up by British intelligence officials who said the extent of the Iranian government’s involvement in activities inside Iraq by a small number of Revolutionary Guards was “far from clear”.

Hillary Mann, the National Security Council’s main Iran expert until 2004, said Pace’s repudiation of the administration’s claims was a sign of grave discontent at the top.

“He is a very serious and a very loyal soldier,” she said. “It is extraordinary for him to have made these comments publicly, and it suggests there are serious problems between the White House, the National Security Council and the Pentagon.”

Mann fears the administration is seeking to provoke Iran into a reaction that could be used as an excuse for an attack. A British official said the US navy was well aware of the risks of confrontation and was being “seriously careful” in the Gulf.

The US air force is regarded as being more willing to attack Iran. General Michael Moseley, the head of the air force, cited Iran as the main likely target for American aircraft at a military conference earlier this month.

According to a report in The New Yorker magazine, the Pentagon has already set up a working group to plan airstrikes on Iran. The panel initially focused on destroying Iran’s nuclear facilities and on regime change but has more recently been instructed to identify targets in Iran that may be involved in supplying or aiding militants in Iraq.

However, army chiefs fear an attack on Iran would backfire on American troops in Iraq and lead to more terrorist attacks, a rise in oil prices and the threat of a regional war.

Britain is concerned that its own troops in Iraq might be drawn into any American conflict with Iran, regardless of whether the government takes part in the attack.

One retired general who participated in the “generals’ revolt” against Donald Rumsfeld’s handling of the Iraq war said he hoped his former colleagues would resign in the event of an order to attack. “We don’t want to take another initiative unless we’ve really thought through the consequences of our strategy,” he warned.