By Paul Reynolds BBC news Online World Affairs correspondent

The whole nature of the debate over Iraq has been transformed by US President George W Bush's decision to go to the United Nations.

The US wants any UN resolution to give it the last say on military action

Mr Bush has managed to cast Iraq, not the United States, in the role of unilateralist.

Those who criticised Washington for ignoring the UN are now criticising Iraq for defying it.

And it will be much easier for Washington to get others to rally behind a military operation.

Urging compliance

Those who would not support the US acting by itself might support the UN acting collectively.

Getting others on board is now the priority for US diplomacy

Speaker after speaker at the General Assembly meeting over the past few days has urged Iraq to comply with the existing Security Council demands on weapons of mass destruction and to allow weapons inspectors back in.

The Jordanian Foreign Minister, Marwan Muasher, said that the people of Iraq could thereby be saved from military action and the region saved from the "dire consequences" of war.

Even Saudi Arabia has suggested that its attitude towards an invasion of Iraq would change if the UN supported it.

Single resolution

But the US still has work to do before it gets the UN to approve any military action.

Powell: Washington would prefer a single UN Security Council resolution

Only Britain has come out clearly in favour of an invasion and "regime change" if the UN route is blocked.

Getting others on board is now the priority for US diplomacy.

US Secretary of State Colin Powell, again at the forefront of US policy after his success in getting the president to give the UN a chance, said on Sunday that Washington would prefer to have a single Security Council resolution.

This would, US officials say, contain an indictment of Iraq for ignoring UN demands, an ultimatum, including a deadline of a perhaps a few weeks for Iraq to comply, and a threat of action if it did not.

Mr Powell accepted that others, including France, wanted two resolutions - first the warning, then the authorisation of action.

He said that he did not rule out any option but Washington fears that having two stages might let Iraq off the hook by opening up a potentially fatal delay in passing a second resolution.

Getting the votes

The US also wants any resolution authorising force to be broadly worded, leaving the final decision on action up to the US and whatever coalition it manages to assemble.

In order to get a resolution passed, the US needs to get nine of the 15 votes on the Security Council and to avoid a veto from any of the five permanent members, which are China, Russia, Britain and France apart from the US itself.

The 10 temporary members are: Mauritius, Mexico, Norway, Singapore, Syria, Bulgaria, Cameroon, Colombia, Guinea and Ireland.

Diplomats think that with a bit of pressure, it is not impossible for the US to get many of the temporary members on its side.

And avoiding a veto is probably not an insuperable problem either.