State-run newspapers and government officials here never used to miss an opportunity to heap scorn on U.N. weapons inspectors, calling them spies, amateurs and opportunists who sought to prolong their work to justify continuing the economic sanctions on this country.

But now that inspectors have returned after a four-year absence for a mission that could determine whether the United States launches military action aimed at toppling President Saddam Hussein, the Iraqi leader appears to have pressed the mute button on the usual rhetoric. The new message is cooperation.

On Wednesday and Thursday, the first two days of resumed inspections, the U.N. experts who set off in their white vehicles and baby-blue hats to search for evidence that Iraq has developed or is developing weapons of mass destruction were received in a way their predecessors never were.

The gates to research complexes and arms factories swung open without delay. Solicitous Iraqi officials let the inspectors poke around, take samples and leaf through documents. The director of an engineering center proudly proclaimed to reporters that he was pleased to receive the inspectors.

U.S. and U.N. officials wonder whether the warm reception will vanish when inspectors attempt to enter one of Hussein's palaces or other sensitive sites. U.S. intelligence officials believe Iraq has moved its weapons programs out of facilities that are known to the inspectors and into new types of structures, including underground bunkers and mobile units.

But Iraqi officials and analysts say that the new attitude is not an act. They contend that Iraq has no prohibited weapons or programs and that Hussein has decided to call President Bush's bluff by doing what nobody outside Iraq ever expected him to do: make nice with the inspectors.

"We're going to surprise the world," one of the president's advisers said.

"We don't like 1441," he said, referring to a U.N. Security Council resolution, "but we will cooperate with it." The resolution, passed unanimously this month, calls for inspectors to be given access to any person or place in Iraq without having to seek permission or give notice.

The two U.N. officials leading the field inspections said they are satisfied with the Iraqi response thus far.

"We've received full cooperation," said one of the leaders, Demetrius Perricos of the U.N. Monitoring, Verification and Inspection Commission. He said he believed "that will remain the case" for visits to the nearly 1,000 sites declared by Iraq over the years as having a connection to nuclear, biological and chemical weapons programs and missile development.

Perricos said Iraq's compliance with the resolution has gone beyond just opening doors quickly. When inspectors inquired on Thursday about a small fermentation tank that was missing from the al-Dawrah veterinary medicine laboratory, plant officials said it had been moved to another facility.

Then, he said, the officials took the inspectors there to see it for themselves.

The officials could have brought the tank to the al-Dawrah plant, a U.N. official said, but the fact they told the inspectors where it was -- allowing them to exercise their power to visit any site they want -- suggested to the experts the Iraqis were not trying to be evasive, at least in that instance.

"They could have handled it very differently," the official said.

Although the inspectors have not provided the Iraqi government with advance warning of the sites they plan to search, they have chosen to make a fairly nonconfrontational start by visiting places that U.N. experts visited in the 1990s.

That strategy likely will continue at least until Dec. 8, when 35 more inspectors are scheduled to join the 17 already on the ground. U.N. officials have said they need more experts to conduct searches of large, previously unexamined sites such as presidential palaces.

Whether Iraq's cooperative posture will change as the searches become more intrusive remains a big unknown. The experts here believe a key test of Iraq's intentions will occur on Dec. 8, the deadline for Hussein's government to make a complete declaration of the status of its chemical, biological, nuclear and missile facilities.

Iraq has said many times that it no longer possesses any banned weapons -- a contention many U.N. officials question. For the claim to be regarded as credible, U.N. officials said, Iraq cannot issue its usual denials and perfunctory reports. "In the past, Iraq has consistently failed to tell the truth," one U.N. official said. "If they really mean to be cooperative, they will have to give us an honest declaration" that makes its point with convincing detail and documentation.

Two British newspapers, the Times and the Independent, citing unidentified British government sources, reported in today's editions that Hussein has ordered weapons of mass destruction to be hidden in the homes of government officials.

The inspectors do not expect to find flagrant signs of banned weapons at the previously searched sites that they plan to visit over the next few weeks. Rather, they regard these first trips as critical in developing a picture of what has occurred in Iraq since the last inspections four years ago.

U.N. inspectors first arrived in Iraq in 1991, shortly after the end of the Persian Gulf War. They have been credited with destroying tons of chemical and biological weapons and dismantling the country's nuclear weapons program. But the monitoring ended in 1998 amid disputes over the inspectors' access to Iraqi sites and Iraqi objections that the United States used some inspectors as spies.

Now, high-level Iraqis say they hope their country's cooperation and the outcome they predict -- that the experts will come up empty -- will be convincing enough to stymie U.S. calls for international military action to disarm Hussein's government and to persuade the Security Council to lift the economic sanctions imposed after Iraq's 1990 invasion of Kuwait.

"While we know America wants to attack us no matter what, we hope that our attitude toward the inspections will convince the world that war is the wrong option," said Mohammed Muthafar Adhami, a member of parliament and the chairman of the political science department at Baghdad University.

An Iraqi soldier stands guard in front of U.N. headquarters in Baghdad, where weapons inspectors have returned after a four-year absence.