U.N. inspectors have yet to turn up any sign of prohibited weapons in Iraq, complicating the Bush administration's task of justifying an armed invasion. Allies already are expressing misgivings, and the inspectors' first comprehensive report, due Jan. 27, could further cramp the timing of any attack.

Even as the Pentagon presses ahead with a massive military buildup in the Gulf, U.S. and British officials are assessing the potential consequences should the report prove inconclusive. That could force the White House into accepting more delay -- or risk the wrath of allies by going it alone.

President Bush asserted Monday that Iraqi leader Saddam Hussein does not appear to be complying with U.N. demands that he disarm. "But he's got time," Bush added.

Earlier, White House spokesman Ari Fleischer said that while "regime change" in Iraq remains U.S. policy, there was still time for Saddam to relent and disarm.

Iraq says it has no weapons of mass destruction. The Bush administration and Britain insist it does -- and is merely concealing them.

In London, British Foreign Secretary Jack Straw suggested the possibility of war had slipped below 50-50. With the North Korean crisis taking international attention, some support for armed conflict with Iraq seemed to be fading.

Further complicating matters for the United States and Britain: the changing membership of the Security Council. Germany, whose Chancellor Gerhard Schroeder has voiced clear misgivings about invading Iraq, is among five countries that have just taken rotating two-year seats.

Talk was building over the need for a second Security Council resolution before moving further down any path of military confrontation.

The Jan. 27 deadline comes a day before Bush's State of the Union address, putting him in a potentially awkward position if the inspectors say they can't find any evidence of weapons programs.

"The United States at that point is going to have to produce its own evidence that there are weapons of mass destruction, or just decide to go ahead anyway," said physicist David Albright, president of the Institute for Science and International Security and a former nuclear weapons inspector in Iraq.

Other than a desire by U.S. planners to wage any Gulf war in the cooler winter months, there's no compelling reason for a hurry-up invasion, Albright said.

"So it starts in March. Or it starts next year. Saddam isn't going anywhere," he said. "And the fact that the inspectors are there bottles up his weapons programs. It puts him on the defensive. He has to hide things carefully. It's very hard to make progress with everybody watching. I think Iraq has become far less of a risk just because the inspectors are there."

With the deadline nearing, U.N. arms experts have increased their manpower and brought in more helicopters to carry inspectors from site to site.

The intensification prompted Saddam to accuse them of engaging in "intelligence work" instead of looking for weapons -- a contention the White House dismissed. "The work of the inspectors needs to continue," Fleischer said.

U.S. officials, and many analysts, suggest there is still a chance that the inspectors may yet uncover weapons activity -- or at least accuse Iraq of a cover-up in the Jan. 27 report.

Some administration officials cling to a long-shot hope that Saddam may yet be overthrown internally. The United States has been dropping leaflets on Iraq urging people to turn over any information on weapons programs and issuing stern warnings to military leaders -- a process intensified last week.

Sen. Sam Brownback, R-Kan., a senior member of the Senate Foreign Relations Committee, said the administration -- after a slow start -- was stepping up its work with Iraqi opposition groups. These groups are helping with pre-invasion intelligence "and afterward, they will help provide an umbrella of a new government in Iraq and a system to start the democratization process," Brownback said in an interview.

He said he's not surprised by the lack of progress of inspectors. "It's a big country, and these are small weapons, easy to hide."

Tens of thousands of U.S. combat troops were heading for the Gulf in a build-up that will double the contingent to more than 100,000 by the end of January and to 200,000 by the end of February. The eventual fighting force could swell to about half the 550,000 U.S. troops amassed in the 1991 Gulf War.

"We certainly prefer voluntary compliance by Iraq," Bush told troops at Fort Hood, Texas, last Friday. "Yet if force becomes necessary ... America will act deliberately, America will act decisively and America will prevail because we've got the finest military in the world," he added.

Few doubted he was eager to see the issue come to resolution.

"While Jan. 27 is not a magic date for going to war, I think there's still a high degree of commitment in the Bush administration to pursue that option," said former Pentagon analyst Michele Flournoy, now with the Center for Strategic and International Studies. "And they will not want to wait additional weeks or months."

She said failure of the inspectors to find anything would hardly be a surprise. "Saddam has had a lot of practice in hiding what he does. He had plenty of time to conceal, to hide, to move programs. This doesn't tell us much -- other than that he's very clever."