Blair is warned of Cabinet revolt if he backs US military action against Saddam Hussein

Tony Blair was warned by cabinet colleagues yesterday of a ministerial rebellion if Britain joins American-led military action against Iraq.

He was told that the hostility among Labour backbenchers over the prospect of strikes against Saddam Hussein's regime was shared at all levels of government.

The threat to cabinet unity surfaced as the UN secretary-general, Kofi Annan, reported a "positive and constructive" atmosphere at the first UN talks with an Iraqi delegation in a year – aimed at securing the return of UN weapons inspectors to Iraq.

The Bush administration is insisting Iraq must comply with the UN demands, or face possible military action. However, US officials confirmed yesterday that the Bush administration is itself split on whether to "finish the job" left undone by George Bush Snr in 1991 or whether to solve the festering Iraqi threat through diplomacy.

Mr Blair chaired a lengthy cabinet debate on Iraq while rumours swept Whitehall of threatened resignations among ministers if British troops became involved in a second front in the war on terrorism.

During frank exchanges, Mr Blair was warned that any action would have to be justified by detailed, overwhelming evidence of Baghdad's development of weapons of mass destruction in defiance of international law.

The strongest cabinet critic of military action is believed to be Clare Short, the Secretary of State for International Development, who was not at yesterday's cabinet meeting. An ally said: "She would want a thorough analysis of what's being proposed." Robin Cook, the Leader of the Commons, is also understood to be prominent among cabinet "doves" on the issue.

Asked after the cabinet meeting whether ministers shared Labour MPs' reservations about attacks on Iraq, he replied: "Lots of people have sometimes contradictory instincts on this."

More than 60 Labour MPs have signed a Commons motion expressing "deep unease" about the looming threat of attacks on Iraq, while a BBC survey of backbenchers indicated that 85 per cent opposed military action.

The simmering discontent follows a hint by Mr Blair that Britain could endorse action by President George Bush, who has named Iraq as one of the three nations comprising an "axis of evil". Mr Blair told MPs this week: "Iraq is plainly in breach of the United Nations Security Council resolution in relation to the accumulation of weapons of mass destruction, and we have to deal with it."

Mr Annan told the Iraqi Foreign Minister, Naji Sabri, in New York yesterday that its government still had no choice but to readmit foreign weapons inspectors if it wants to escape international sanctions imposed after its 1990 invasion of Kuwait.

But, although Mr Sabri described the first round of talks as "positive", it remains to be seen whether the new Iraqi flexibility will be enough to satisfy the Americans, who can point to years of military stand-offs over the Iraq arms inspections.

Mr Blair will meet Mr Bush for talks about Iraq at the President's Texan ranch between 5 and 7 April. The US Secretary of State, Colin Powell, said he did not know of "any plans that would be on his [the President's] desk" concerning military action against Iraq when Mr Blair visits.