British Prime Minister Tony Blair has promised to publish evidence on Iraq's alleged development of weapons of mass destruction as international scepticism grows over the justification for a strike against Baghdad.

In the broadest indication to date that he supports a campaign against Baghdad, Mr Blair declared that the regime must start to function in an "entirely different way" or would "have to change".

Weapons inspectors should go back in - unconditionally - any time, any place, anywhere, under a weapons inspectors regime that really makes a difference

Tony Blair

He said the dossier would be published in the next few weeks.

Mr Blair spoke shortly after Iraq said it might consider re-admitting UN arms inspectors - but only as part of a wider agreement which respects Iraqi sovereignty and brings an end to UN sanctions.

Mr Blair said there was no room for bargaining over the return of the UN arms mission, which has been barred from Iraq since 1998.

"Weapons inspectors should go back in - unconditionally - any time, any place, anywhere, under a weapons inspectors regime that really makes a difference."

"If the Iraqis refuse that, then we have to find a different way of dealing with it," said the British premier, who has positioned himself as America's closest European ally on the issue of Iraq.

Just after he made the speech, US Defence Secretary Donald Rumsfeld said President George W Bush may also make evidence on Iraq public this month.

'Ultimatums'

Mr Blair did not give details of the evidence that he would be releasing, but his decision to release a dossier comes as public opinion in Britain and abroad becomes increasingly hostile toward the possibility of a US strike.

However, he did imply that there was no proof that Iraq had its hands on nuclear weapons, although he said he "believed" there was evidence that the country would acquire such weapons "if they possibly can".

A string of countries want more pressure to be applied on Iraq to admit weapons inspectors before any campaign is considered and on Tuesday Iraq's Deputy Prime Minister Tariq Aziz said his country was ready to cooperate with the UN to find a solution to the crisis.

Mr Aziz told journalists after his meeting with UN Secretary General Kofi Annan in Johannesburg that Iraq "could consider" allowing arms inspectors back but only as part of a "comprehensive settlement" that would see the end of economic sanctions and threats from Washington.

But he also told Mr Annan that Baghdad was "preparing to defend itself" form the threat of a US attack.

Tariq Aziz said Iraq might consider a deal over inspections

And in what has been hailed as a masterful performance for US television, Mr Aziz told Americans they were "making an ultimatum, and ultimatums are not accepted in international law".

"They are an arrogant, imperialist position which cannot be accepted."

The BBC's Middle East analyst says Iraq is hoping to exploit a moment of diplomatic opportunity with much of the world opposed to a US attack on Iraq and with mixed messages coming from Washington.

US Defence Secretary Donald Rumsfeld dismissed Mr Aziz's overture as a "ploy" and accused Iraq of playing "the international community and the UN process like a guitar, plucking the right string and the right process at the right moment".

At a news conference, he also forcefully denied media speculation that there was a split in the Bush administration over Iraq.

In recent days, US Secretary of State Colin Powell has said that if Iraq allows UN inspectors back in, it would be a "first step", but Vice-President Dick Cheney has insisted there is no point in sending inspectors back to Iraq, arguing forcefully for military action.