WASHINGTON - After seven weeks on the ground in Iraq, United Nations inspectors have yet to find any solid evidence to back up American and British allegations that Iraq is hiding weapons of mass destruction, raising questions about the quality of U.S. intelligence and widening a gap between the United States' rapid war preparations and its ability to justify a military attack.

To Bush administration officials, the failure to uncover any banned weapons is further proof that President Saddam Hussein does not intend to disarm voluntarily as required by the U.N. Security Council, despite Iraq's apparent willingness to allow the inspectors free rein.

But to diplomats from other countries, even close U.S. allies, the lack of damaging evidence against Iraq underscores the need for the arms inspectors to be given more time and for the United States to make a stronger case - or risk going to war without U.N. approval and with minimal foreign support.

"In order to justify military action, there has got to be a very persuasive case. The case has not been made," said a Western diplomat on the Security Council.

This view conforms with U.S. public opinion, which polls indicate offers only soft support for a war and that Americans want not only evidence to justify an attack, but also U.N. approval and allied participation.

"If we don't have Security Council approval or some 'smoking gun,' something incriminatory, it's going to be really tough," said Steven Kull, who studies U.S. public opinion at the University of Maryland's Program on International Policy Attitudes.

The chief U.N. weapons inspectors, Hans Blix and Mohamed ElBaradei, are expected to give a mixed report on their findings to the Security Council today. On one hand, U.N. officials say, they will cite serious gaps and apparent errors in Iraq's Dec. 7 declaration, which was supposed to contain an "accurate, full and complete" account of Iraq's programs to develop nuclear, chemical and biological weapons, as well as missiles with a range beyond the 90 miles permitted by the United Nations.

At the same time, however, both men are expected to say that Iraq has not tried to obstruct their inspections, even at sites that Iraq has tried to put off limits in the past. U.N. officials acknowledge that the resumed inspections have not uncovered damaging evidence against Iraq.

The hunt for proof

The results to date have bolstered the fears of Washington hawks that, by seeking U.N. Security Council support, the United States risked falling into an "inspections trap" involving a prolonged search for weapons that would delay indefinitely any military action to topple Hussein's regime.

As U.N. inspections got under way in November after a four-year hiatus, U.S. officials laid out an aggressive scenario under which inspectors, provided with American intelligence, would "expose Iraqi deception," or probe sensitive areas that would trigger Iraqi attempts to block the inspections, giving the United States the grounds for military action.

U.S. officials have publicly pressed U.N. inspection teams to spirit Iraqi scientists out of the country, a move likely to raise alarm in Baghdad over the loss of valuable secrets.

Despite American promises, the kind of intelligence that could give the inspectors valuable leads was slow in coming, prompting one U.N. official to say this week: "There are people who wonder whether there is targeted or concrete information available."

ElBaradei said recently that the International Atomic Energy Agency, which he heads, had not received "actionable" intelligence.

In an apparent dig at Washington, France's foreign minister, Dominique de Villepin, wrote yesterday to the 14 other members of the Security Council, saying that inspectors must be given "all the means they need for their work to be fully effective."

U.N. inspectors, a French official said, have "complained that what they received was vague and too general to be used."

U.S. officials insist that they have been providing intelligence to inspectors, but say they are limited in what they can turn over by concern that sources and methods used to obtain the information might be compromised. For several weeks, the inspection agencies were not fully geared up and ready to act on the intelligence, the officials said.

A senior U.S. official acknowledged that it was only last week that Blix's team received a package of information about "a number of sites in a variety of areas."

Because Blix and his director of planning and operations, Demetrius Perricos, were on vacation, inspectors have not yet inspected the sites. The inspections require careful planning and "skillful execution," the U.S. official said. "These are not trivial sites. It's not easy to do."

The official acknowledged that even with this new intelligence, the inspectors might not be able to find proof.

"Saddam Hussein has gone to great lengths for a dozen years to hide" his programs, the official said. "We've always said the inspectors may not find anything."

Despite the Iraqis' cooperation thus far, the pressure on them will likely mount. Armed with eight helicopters, a laboratory in Baghdad and a second headquarters in Mosul in northern Iraq, inspectors can conduct surprise inspections further afield. Toward the end of this month, the IAEA will get lab results on dust samples that could indicate past or current nuclear activity.

Filling the gaps

Late next week, Blix and ElBaradei plan to go to Baghdad to press Iraqis to fill gaps in the Dec. 7 declaration. The inspectors want to know what happened to about 6,000 chemical warheads apparently left over from the Iran-Iraq war and unaccounted-for nutrients capable of producing thousands of gallons of germ agents. Blix has evidence that may contradict Iraq's claim that it has no active biological weapons program.

Iraq has raised suspicions with numerous attempted or completed foreign purchases of equipment that can be used to produce weapons of mass destruction, including uranium (which can be enriched for nuclear arms) from Niger, vacuum pumps and "lithotripter" machines with precision electronic switches suitable for bombs.

Experts say that if Iraqi officials fail to provide adequate explanations, Blix and ElBaradei could charge them with failure to cooperate when the chief inspectors give a more complete report to the Security Council on Jan. 27. That, in turn, could be used by the United States to persuade the council that Iraq is in "material breach" of U.N. mandates - legal grounds for the "serious consequences" threatened in the council's Nov. 8 resolution.

While ElBaradei says that months of additional inspections are needed to know for certain whether Iraq has disarmed, the Bush administration is looking to the Jan. 27 meeting as a turning point.

U.S. officials insist that the burden remains on Iraq to disclose its weapons programs and disarm - not on the United States or the inspectors.

"It's not necessary that we go and find a storage facility of biotoxins or whatever," a senior U.S. official said. "Anyone who has looked at the evidence can see that they have weapons they failed to declare - missiles, chemical and biological, and efforts to reconstitute their nuclear program."

Said another: "It should be very clear by the 27th whether Iraq is willing to comply. Once they've heard from Blix and ElBaradei on the 27th, council members will have to make a decision about what they think of Iraqi compliance or noncompliance. We'll have to go from there."