After five weeks in Iraq, U.N. weapons inspectors have rebuilt an operation that lay fallow for four years and, by Iraqi count, checked out 230 sites in a blitz of searches uninterrupted by weekends or holidays. Now the inspectors are ready to step up the pace even more, using helicopters to descend swiftly on suspect sites and opening a regional office to widen the hunt for banned arms or research programs.

But Iraqi officials maintain that the operation has yet to turn up any proscribed weapons and, privately, some U.N. officials agree. "If we'd found a shed full of Scud missiles, don't you think we would have reported it to the [Security] Council?" said a U.N. official who asked not to be identified.

That does not mean that inspectors have not found subtler clues that, added together, might point to violations -- "precursor" chemicals that could be used to develop weapons, for example, or aluminum tubes that could be used in enriching uranium. And the Bush administration, which insists that Iraq possesses banned weapons, has pledged to provide intelligence to help the inspectors find what they are looking for.

But if inspectors do not produce more conclusive proof in the days and weeks to come, the United States might find it difficult to convince other nations of the need to go to war against President Saddam Hussein's government. The U.N. inspectors have just a week before their chief, Hans Blix, must deliver a status report to the Security Council and 18 days more before he presents findings under the Nov. 8 council resolution mandating Iraqi cooperation with the inspections.

Iraqi officials said today that Blix has accepted an invitation to return to Baghdad in the third week of January to talk about "pending issues" -- in effect, a last chance to satisfy his concerns before making his conclusions to the Security Council on Jan. 27.

In the meantime, the inspection force has assembled a fleet of six U.S.- and Russian-made helicopters to begin exploring the country from the air and pouncing on faraway sites with greater surprise. On Saturday, it expects to open its first branch office, in a hotel in Mosul, about 240 miles north of Baghdad.

Until now, Iraq has responded to the inspection process with calm cooperation, opening every door with virtually no significant delays or trouble. Yet as it becomes clear that the United States is sending more troops to the Persian Gulf region despite lack of new evidence, Iraqi officials have grown increasingly irritated with the U.N. team and stepped up the anti-American rhetoric they had largely eschewed at the beginning of the inspections.

In the last few days, directors of facilities have bristled at the behavior of the inspectors. One complained that they stormed into his missile plant like "a gang." Another groused about an unannounced visit on New Year's Day, when everyone was off on holiday. Yet another complained today that the repeated visits were interrupting his staff's work.

Gen. Hussam Mohammed Amin, the chief Iraqi liaison to the U.N. team, endorsed the grievances. "We think with him that this entry was provocative and touching our dignity," he said today, referring to the "gang" complaint. "When you come to my house and you want to visit my house, you can say, 'Please, good morning, I want to visit this room or that room.' . . . When you go directly without apologizing and running inside the site . . . this is unacceptable really and touching the Iraqi sensitivities and Iraqi feelings."

Amin said his scientists had shadowed the inspectors everywhere they went and could determine for themselves that the U.N. team had found no violations. His conclusion was backed up by recent comments of an inspector who told a Los Angeles Times reporter that "we would have zilch to put" in any report now.

Yet the latest news of planned U.S. troop movements appears to have convinced Iraq that the inspections will not sway Washington. "They didn't say, 'Let us wait for a while for the result of the inspection and then let's decide what to do,' " Deputy Prime Minister Tariq Aziz told visiting Spanish peace activists today. "When they continue their preparations for the war of aggression, what does that mean? It doesn't mean that they are genuinely afraid of an imaginary Iraqi threat. It means that they have an imperialist design."

Readmitting the inspectors was a calculated risk by Hussein's government that it could avoid a U.S.-led attack by displaying cooperation. But the government created a difficult position for itself when officials issued categorical statements denying any current development of ballistic missiles or chemical, nuclear or biological weapons, leaving themselves no room to make concessions and making the government vulnerable if anything were found.

A foreign official working here said he still expected Iraqi officials to find a way to walk back that absolute denial and admit a little here or there as a strategic way to ease the pressure, just as they did during the seven years that inspectors operated in Iraq before withdrawing under pressure in 1998. A diplomat concurred that the Iraqis still have some moves left. "There will be more [concessions]. Definitely there will be more," he said. "This is a chess game being executed on 10 levels at the same time."

Mohammed Muthafar Adhami, dean of political science at Baghdad University and a member of the Iraqi parliament, said the strategy was to divide the United States from its allies by going along with inspections. "The most important thing is to keep cooperating with the inspection teams," he said. "If there is any breach of [U.N. Resolution] 1441, it means war. At least, that's the American point of view."

Iraq has played host to a stream of peace delegations arriving from Europe and the United States. Aziz met with a group of U.S. religious leaders who spent the last few days visiting schools, hospitals and other locales here, then issued a statement today condemning a potential war against Iraq as "completely antithetical" to the teachings of Jesus.

"Preemptive war is immoral and illegal," said Bob Edgar, general secretary of the National Council of Churches and a former member of Congress from Pennsylvania. "It is theologically illegitimate and profoundly violates our Christian beliefs and religious principles."

Melvin G. Talbert, a United Methodist bishop who joined a similar mission just before the Persian Gulf War of 1991, said he was struck by the difference in Aziz's tone. "This time he was much more cordial," Talbert said. "This time he was understanding of the importance of our being here. . . . He understood that the image of Iraq in our country is a negative one and we're here to put a positive spin on things."

Staff writer Colum Lynch at the United Nations contributed to this report.

A U.N. inspector talks to an Iraqi official at the Fatah factory in Baghdad. At some facilities, directors have grown irritated with the arms inspections.Gen. Hussam Mohammed Amin, chief Iraqi liaison to the U.N. team, said his scientists shadowed the inspectors and could tell no violations were found.