WASHINGTON - US Defence Secretary Donald Rumsfeld on Tuesday left open the possibility that the United States might invade Iraq without the help of British forces, but said that decision would have to be made by President George W Bush.

"That is an issue that the president will be addressing in the days ahead, one would assume," he said when pressed at a Pentagon news conference on whether Washington might go ahead without its closest ally.

The United States and Britain currently have more than 250,000 troops gathered in the Gulf region around Iraq, but British Prime Minister Tony Blair has come under mounting anti-war pressure at home.

Rumsfeld was asked by reporters whether the United States, with about 225,000 of its troops already in the Gulf region and thousands more on the way, might go ahead without Britain or whether Britain might scale back its participation.

"This is a matter that most of the senior officials in the government discuss with the UK on a daily or every other day basis," said the secretary, adding that he had spoken on the telephone with British Defence Minister Geoff Hoon "about an hour ago."

Meanwhile the United States called for a UN vote authorising war against Iraq by the end of this week, but there was little sign that a proposal to extend an ultimatum to Baghdad for a few days could win a Security Council majority.

White House spokesman Ari Fleischer declared: "The vote will take place this week ... There's room for a little more diplomacy here but not much room and not much time."

Bush has pledged to go to war with or without UN backing, but the United States is clearly reluctant to abandon efforts to win a Security Council resolution that would give its military operations added legitimacy under international law.

Cameroon's UN ambassador Martin Belinga-Eboutou said the Security Council's six undecided nations had proposed a 45-day deadline for Baghdad. But Fleischer dismissed even a month-long extension as a non-starter.

"Don't look beyond March," Britain's UN ambassador, Sir Jeremy Greenstock, said.

Even if France and Russia carried through their threat to veto such a resolution, it could provide some much-needed political cover for loyal US allies, British Prime Minister Tony Blair and Spanish Prime Minister Jose Maria Aznar. They both face public opinion that is overwhelmingly hostile to war without UN approval.

After a day of dramatic public developments on Monday, most of the action took place behind closed doors on Tuesday. UN officials said they were waiting to see what the British and Americans came up with but the allies did not share their thoughts with the uncommitted nations.

Security Council members were due to hold an open meeting on Tuesday afternoon to give more countries a chance to air their views on the crisis. Several nations were expected to take the opportunity to criticize the United States.

The United States and Britain so far have failed to muster more than four of the nine votes needed for passage of a resolution setting a March 17 deadline for Iraq to satisfy them that it is fully disarming or face attack.

Bush called the president of Security Council member Angola, Jose Eduardo Dos Santos, kicking off a hectic day of telephone diplomacy. Angola is one of six Security Council members still uncommitted, the others being Chile, Mexico, Pakistan, Guinea and Cameroon.

In a televised address to the nation, Pakistani Prime Minister Mir Zafarullah Khan Jamali made no specific mention of Pakistan's voting plans, but said: "It would be very difficult for Pakistan to support war against Iraq. This goes against the interests of my nation and of my government.

Five nations, three of which have veto power, are definitely against the resolution: Russia, France, China, Germany and Syria. Those in favour are the United States, Britain, Spain and Bulgaria.

Blair is facing the worst crisis of his leadership and indicated that he might be willing to extend the March 17 ultimatum a little but British officials said they would not let the issue drag out beyond the end of March.

He criticised France and Russia for threatening to use their veto, saying they were encouraging Saddam to stand firm and not give into UN demands.

In the potential war zone itself, unconfirmed reports from travellers arriving in Iraq's Kurdish zone said Iraq had mined its northern oilfields of Kirkuk and dug a huge oil-filled trench around the city. Iraq has denied this.

Iraq has begun destroying more al-Samoud 2 missiles, meaning almost half the Iraqi arsenal of the prohibited rockets have now been broken up.

UN arms inspectors suspended U-2 reconnaissance flights over Iraq for safety reasons after Baghdad complained two aircraft flying simultaneously was a hostile action.

A senior Iraqi official said the United Nations had admitted that having the second aircraft in the air was a "mistake". But US officials said that under UN provisions there was no limit on the number of surveillance planes they could fly at any one time.

Baghdad has denied accusations it is hiding weapons of mass destruction and says it is cooperating with UN inspectors.

- REUTERS