Foreign Secretary Jack Straw said Tuesday that Britain reserved the right to take military action against Iraq without a second UN resolution.

Straw reiterated that if Iraqi President Saddam Hussein defies an existing United Nations resolution on disarmament, Britain's preference was for the UN Security Council to pass a second resolution authorizing military action.

Britain's preference "is that we have a second Security Council resolution...which we want...we've had to reserve our rights if we can't achieve that," Straw told BBC Radio.

He recalled that the British Parliament late last year backed a motion that reserved "the right to deal with the matter without a United Nations resolution if that was the situation." The government's position has not changed since then, he said.

Britain and the United States say they know Saddam has weapons of mass destruction and say he must disarm or be disarmed by force. A United Nations resolution threatens Saddam with "serious consequences" unless he comes clean about suspected weapons of mass destruction.

AFP adds: The United States denied Monday having a specific timetable for war as more US troops headed for the Gulf and Britain challenged Iraq's Saddam Hussein to "take the peaceful route and disarm."

Some 150,000 US ground, air and naval forces are expected to be prepared to attack Iraq by mid-February, but the White House insisted President George W. Bush had set no timetable for war.

Aides seemed to caution crystal-ball gazers against viewing January 27, when UN disarmament inspectors will report their findings to the UN Security Council, as a trigger date.

"The president thinks it remains important for the inspectors to do their job and that they have time to do their job. The president has not put an exact timetable on it," said Bush spokesman Ari Fleischer.

State Department spokesman Richard Boucher echoed those comments, saying the only issue that mattered was stripping Saddam of any nuclear, chemical or biological weapons. Baghdad denies having such arms.

"The issue is not some arbitrary period of time," he said. "The issue is Iraq's disarmament."

Bush, who has vowed to disarm Iraq by force if necessary, could further build his case for invasion during his annual "State of the Union" speech to the US Congress and the nation, expected January 28.

Fleischer's comments came after International Atomic Energy Agency Director General Mohamed ElBaradei said in Paris that UN inspectors hunting for any weapons of mass destruction needed a few more months to determine whether Iraq has a secret weapons program in defiance of the world body.

ElBaradei and chief UN weapons inspector Hans Blix are due to deliver a progress report to the UN Security Council January 27, and are coming under increasing pressure from Washington to show results.

The UN inspectors' field boss, Dimitris Perrikos, indicated his teams would soon begin surprising the Iraqis with unannounced searches of suspect facilities.

"It is true the Iraqis are opening the doors, but they are opening installations they know we are aware of. The test will be when we start going to facilities where they will be surprised," Perrikos said in an interview with Greek newspaper Ta Nea.

In London, British Prime Minister Tony Blair -- a key US ally -- challenged Saddam to "take the peaceful route and disarm.

"If he does not, he will be disarmed by force," Blair said.