By Barnaby Mason BBC diplomatic correspondent

Senior US and British officials are visiting France, Russia and China on Friday and over the weekend to try to get their backing for a tough new United Nations Security Council resolution against Iraq.

Chirac (r) is attempting to co-ordinate his objections with Russia and China

All three countries have shown reluctance to give the US a green light for military action before UN weapons inspectors have had time to establish whether Iraqi President Saddam Hussein still has weapons of mass destruction.

And the latest diplomatic drive indicates that it is not possible to overcome French, Russian and Chinese resistance through negotiations at the UN or telephone calls alone.

A senior US State Department official, Marc Grossman, is taking the argument to Paris and Moscow, accompanied by the British Foreign Office's top negotiator, Political Director Peter Ricketts.

Another senior British official, International Security Director William Ehrman, is travelling to Beijing over the weekend.

'Uphill trek'

They will show the governments of France, Russia and China the draft resolution agreed between Washington and London, then talk them through the long, strong and detailed text, as British officials described it.

The US may yet compromise over the issue of two UN resolutions

The officials said it would be an uphill trek to achieve an agreement, echoing an earlier comment by the US Secretary of State, Colin Powell.

To illustrate the intensity of discussion, they said the British Foreign Secretary, Jack Straw, had had eight phone conversations with Mr Powell in the last five days.

For his part, French President Jacques Chirac has been trying to co-ordinate his objections with Russia and China.

His spokeswoman said they shared the same approach, noting that China approved the French concept of two Security Council resolutions.

Only the second would authorise military action.

Compromise?

France, Russia and China also do not want to agree now to a resolution under which the slightest Iraqi prevarication would be an automatic trigger for military action.

But that seems to be precisely what the Bush administration wants, though diplomats say the language has been toned down on Britain's advice.

The French want to maximise their own influence, and two resolutions separated in time would achieve that.

It is conceivable the Americans might compromise on this point.

As for the Russians and Chinese, they are likely in the end to define their prime interests in terms of their relations with the US.