High-level Iraqi officials pledged today to provide "full cooperation and full transparency" to U.N. experts trying to determine whether Iraq still possesses weapons of mass destruction, a senior U.N. official said, raising hopes among an advance team of inspectors that their mission could be spared the evasions that plagued previous efforts to hunt for banned weapons.

The inspectors logged their first full day of work here, with about two dozen technicians starting to rehabilitate offices that have lain dormant since 1998, when the previous inspectors left Iraq. The two U.N. officials responsible for the process, chief weapons inspector Hans Blix and Mohamed ElBaradei, director general of the International Atomic Energy Agency, met with senior Iraqi officials, including Foreign Minister Naji Sabri and Gen. Amir Saadi, a presidential adviser coordinating Iraq's inspections policy.

Blix and ElBaradei said they left their meetings feeling optimistic that Iraqi officials understood the gravity of the situation and that they would attempt to comply with the rigorous inspections mandated by a U.N. Security Council resolution passed unanimously Nov. 8. Iraqi officials also promised to meet a Dec. 8 deadline set by the resolution for providing a full account of Iraq's chemical, biological and nuclear facilities and programs, they said.

"Within 30 days, as the resolution says, a report from Iraq will be submitted on all the files, nuclear, chemical, biological and missile files. . . . We are hopeful. We are in fact quite sure that things will work out much better than before," Saadi told reporters here.

Although Blix and ElBaradei said Iraq's pledges can be evaluated only after spot checks begin this month, the U.N. mission has clearly commenced on far more amicable footing than previous attempts, with both sides saying they would do their utmost to work with each other. U.N. officials and diplomats here said the tenor of the comments from the Iraqi officials could mean that after years of hindering inspections, President Saddam Hussein has concluded that acceding to weapons searches, no matter how intrusive, provides him the best chance of averting an attack by the United States.

"In our meetings today, all Iraqi officials have committed to provide us with full cooperation and full transparency," ElBaradei said at a news conference with Blix.

"We heard today from the Iraqi side that they will do -- and I think I'm quoting them correctly -- that they will do everything that is humanly possible to cooperate with both organizations to move forward," ElBaradei said. "We hope that we'll see that commitment translated into reality when we start our inspections."

During the first two days of their three-day visit to Baghdad, Blix and ElBaradei have refrained from delivering public warnings to Iraq that they will not tolerate attempts to interfere with their work. Instead, they have emphasized their desire to be objective and unbiased, and they have said that compliance would result in the lifting of U.N. trade sanctions imposed in 1990, something that Iraq has long sought.

Iraqi officials have expressed a desire to have the inspections finished quickly, voicing frustration that previous rounds lasted for more than seven years without a major change in the sanctions, except for a program that allows the country to sell its oil for humanitarian supplies.

U.S. and U.N. officials have said the inspections dragged on because Iraq repeatedly lied to the inspectors and blocked their work. But ElBaradei said today, "If Iraq cooperates fully, we can foresee reporting within one year that Iraq has fulfilled the requirements" of Security Council resolutions requiring it to disarm.

Blix and ElBaradei's conciliatory approach has differed from that of the Bush administration, which is pushing for early, intrusive inspections of presidential palaces and other sensitive sites. But aides to both men said it is essential to first build trust between the inspectors and the Iraqis.

"We've told them we're on a mission of peace," said Mark Gwozdecky, a spokesman for the IAEA. "We've tried to tell them that we want a fresh start and that cooperation is the best way to achieve a peaceful resolution."

One example of the differing approaches concerns antiaircraft fire on U.S. and British warplanes. In recent days, U.S. officials have asserted that Iraqi efforts to shoot down planes patrolling "no-fly" zones in northern and southern Iraq constitute a breach of the resolution. Iraq considers the patrols a violation of its sovereignty and frequently shoots at allied planes.

U.N. Secretary General Kofi Annan took issue with the Bush administration's interpretation, telling reporters in Kosovo: "I don't think the council will say that this is in contravention of the resolution that was recently passed."

Iraq's declaration of its weapons programs and civilian chemical, biological and nuclear activities was the focus of much of today's discussions between the inspectors and their Iraqi counterparts, U.N. officials said. The Iraqis questioned how comprehensive they needed to be in what they submit and whether unintentional omissions would be held against them, the officials said.

"They're saying, 'We've got chemical factories of every size, shape and description. We've got plastic factories and paint factories. How are we supposed to report on every one of these?' " a U.N. official said.

The U.N. official said Blix and ElBaradei told the Iraqis that they should direct their queries to the Security Council, not the inspectors. "We told them that only the Security Council can interpret its [own] words," the official said.

Iraq has long insisted that it no longer possesses weapons of mass destruction. But Blix suggested its officials take another look, indirectly pointing at a possible way to save face if Hussein's government feels it needs to revise its stand. "We have tried to impress upon them to look into their stocks and their stores to see if there is anything that should be declared," Blix said.

Blix said he also talked to Iraqi officials about opening a satellite office in the northern city of Mosul and expanding the inspectors' offices in Baghdad.

Chief inspector Hans Blix looks on as IAEA director Mohamed ElBaradei speaks to reporters.