The US secretary of state has said Washington will begin circulating a draft resolution on giving the UN a bigger role in Iraq to Security Council members in the next few days.
Polish-led soldiers are now in charge of security in parts of Iraq
Colin Powell said after contacting the foreign ministers of Russia, France, Germany and the UK that initial reaction to plans, which include transforming the coalition into a UN-approved multinational force, had been "positive".
"We are asking the international community to join us," he told reporters.
In America, concern over the costs of the occupation is mounting while in Iraq itself the US-led coalition is under criticism for failing to prevent recent terror attacks.
Mr Powell said the new resolution would ask for the creation of a multinational force under unified, American command.
It would also ask the US-backed Governing Council (GC) in Iraq to draw up an election timetable.
While the US would retain the "dominant" role politically and militarily, the UN would have roles to play in such areas as reconstruction and organising elections, he added.
Officials in London predicted no "sudden dramatic vote within days" at the Security Council but it is widely believed that America wants a resolution tabled before President Bush addresses the UN General Assembly in three weeks' time.
The BBC's David Bamford at the UN says the scene is set for hard bargaining with much concern that the new resolution should not be seen to endorse American actions in Iraq so far.
On Wednesday, the US transferred responsibility for security duties in a region of central Iraq to a 21-nation force led by Poland.
Marines formally handed over control of the area, which includes the troubled city of Najaf, to Polish commanders at a ceremony in Babylon.
The idea of asking the UN to give legitimacy to the US-led occupation of Iraq has been bitterly opposed by Bush administration hawks, says BBC Washington correspondent Justin Webb.
But, he adds, President Bush now appears ready for compromise if it means the burden of reconstruction can be shared.
The US Congressional Budget Office warns that the number of American troops in Iraq will have to be more than halved if threats elsewhere in the world are to be confronted.
Iraq operations currently cost the US about $3.9bn a month.
US officials have been meeting colleagues from the European Union, Japan and the United Arab Emirates in Brussels to discuss Iraq's reconstruction.
International aid donors at the meeting expressed concern about the deteriorating security situation in Iraq.
Representatives of the UN, the World Bank and Iraq's GC are also present at the talks, designed to lay the groundwork for a formal international donors' conference in October.
The US chief administrator in Iraq, Paul Bremer, has said he is willing to give more authority to GC members once they consolidate their position.
The emergence of Iraqi militias indicates growing impatience with the US administration
But one GC member, Shia Muslim leader Muhammad Bahr al-Ulloum, has suspended his participation and threatened to set up armed militias, accusing the coalition of failing to provide adequate security.
He acted after Shia cleric Ayatollah Muhammad Baqr al-Hakim and more than 120 other Iraqis were killed by a bomb in Najaf on Friday.
Mr Bahr al-Ulloum told the BBC Arabic Service that such militias would be in charge of security in holy places in the cities of Najaf and Karbala.