The prime minister has told the Commons he is confident that the UN will back plans to strip Saddam Hussein of this weapons of mass destruction.

His comments came after Downing Street said a new UN security council resolution on Iraq should be expected in weeks rather than days.

During prime minister's questions, Tony Blair told the Liberal Democrat leader, Charles Kennedy, that it should be possible to deal with the Iraq crisis through the UN.

In the wake of the Bali bombing, Kennedy had warned that an American-led assault on Iraq without United Nations support could fracture the international coalition against terrorism.

Pressing Blair on fears of a unilateral strike against Saddam Hussein, Kennedy said any military action should be carried out through the UN.

The PM told Kennedy he was "not going to speculate" on possible action against Iraq, but said he was working to hold the international coalition together.

"I want to see us proceed on the broadest possible basis of consent," he said.

The prime minister repeated his position that the UN must be a way to deal with the Iraqi threat, not avoid dealing with it.

"That's why we've got the process under way at the moment in the United Nations," he said.

"I believe that we will achieve a consensus on this internationally and the reason for that is that most people, when they reflect upon it, do understand that weapons of mass destruction are an issue, do understand that it is not safe for the world to have chemical, biological, potentially nuclear weapons and do understand that the world community has got to make it clear that he's got to be disarmed of those weapons.

"I hope that it is done through the UN and that is what I am trying to achieve."

Kennedy warned the prime minister that action outside the UN could have dire consequences.

He said that the international coalition against terrorism "could begin to fracture if unilateral action was taken against Iraq".

The prime minister said he "certainly understands the concerns that people have about unilateral action against Iraq".

But he warned that "despicable" regimes could be allowed to develop weapons of mass destruction in contravention of security council rules.

"I believe that where the United Nations' authority has been flouted in that way we have a duty to act," said Blair.

Earlier in the day, the prime minister had been quizzed by critics of military action at the weekly meeting of the Parliamentary Labour Party.

Jeremy Corbyn, a longstanding critic of war, said the prime minister had not reassured backbenchers. "I'm not sure how successful he was," he said.

Meanwhile, Number 10 moved on Wednesday to dampen speculation that the UN was close to agreeing tough new orders compelling Baghdad to admit weapons inspectors.

The move followed weekend press reports that UN agreement on tackling Saddam Hussein would be published in "the next few days".

But the prime minister's spokesman told journalists that the wheels of the international community took time to grind into action.

"Whenever the UN process started we did warn that these UN resolutions do take weeks rather than days to put together," he said.

Number 10 said the West would have to "be patient and wait for a result".

Washington is seeking a new UN resolution granting weapons inspectors search powers to uncover Iraq's biological and chemical weapons.

In the event of Saddam's expected defiance, a second resolution would give a US-led coalition authorisation for military strikes.