Some 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. Up to five generals and admirals are willing to resign rather than approve what they consider would be a reckless attack. A generals' revolt on such a scale would be unprecedented. 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". A second US navy aircraft carrier strike group led by the USS John C Stennis arrived in the Gulf last week. 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".