The US administration is urging a strong stance by the United Nations Security Council, despite Baghdad's offer to allowed unconditional weapons inspections.

Mr Bush, who is on Thursday sending a resolution to Congress seeking authorisation for the use of force against Iraq, said negotiations with the Iraqis were over.

Officials say the president hopes to secure "maximum flexibility" from Congress.

Mr Bush said the Security Council must deal firmly with Iraqi leader Saddam Hussein, whom he called "a threat to world peace".

"If the Security Council won't deal with the problem, the United States and others will," he added.

Mr Bush was speaking after talks at the White House with Secretary of State Colin Powell, to discuss a draft resolution on Iraq that is being negotiated at the UN.

Show of resolve

Meanwhile, senior members of Congress have made clear they will back the congressional resolution sought by the administration.

Bush: Congressional resolution will send a vital message

But they have also warned that some Democrats may vote against it.

Mr Powell and Defence Secretary Donald Rumsfeld, for their part, are lobbying for action against Iraq in a series of meeting with senior members of Congress.

The BBC's Justin Webb in Washington say that with UN diplomats now saying it could be the end of October before any inspectors set foot in Iraq, and the end of the year before they begin work, President Bush is struggling to keep up the pressure on Saddam Hussein.

His plan is to have both Houses of Congress pass a special resolution within the next two weeks, authorising the White House to use all appropriate means against Iraq.

Democratic Party members are due to meet on Thursday to try to agree a common position.

Party leaders - who say they will back the resolution drafted by the White House - have warned that some Democrats may oppose it.

Our correspondent says the administration needs to keep the "No" vote as small as possible if the resolution is to be used as a proof to the world of American resolve.

Council split

As the US appeared to move closer to a military option, UN Secretary General Kofi Annan urged Iraq to co-operate with the inspectors.

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In a meeting attended by Hans Blix, the chairman of the UN Monitoring, Verification and Inspection Commission (Unmovic), Mr Annan told Iraqi Foreign minister Naji Sabri he hoped the process of disarming of weapons of mass destruction could be completed as soon as possible.

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Baghdad's agreement to allow arms inspectors to return "without conditions" appears to have split the UN Security Council.

The US and the UK are pushing for a new resolution backed up by the threat of military action.

However Russia said no new resolution was necessary, and urged the "speedy return" of inspectors to Iraq.

Despite the diplomatic moves, the US is continuing to shift military hardware close to Iraq, apparently in preparation for a possible strike.