Iraqi officials told chief U.N. weapons inspector Hans Blix today they have found four more empty chemical warheads, Blix said after holding meetings here to warn President Saddam Hussein's government that "time is running out" for it to increase its cooperation with inspectors.

The disclosure of the four warheads with internal plastic sleeves, designed to fit atop 122mm rockets and disperse deadly sarin gas, has both encouraged and concerned Blix, who said he welcomed efforts by Iraq to search for the munitions and to admit their existence but questioned whether the finding could be the "tip of an iceberg" of undeclared weapons.

On Thursday, inspectors visiting an army munitions depot southwest of Baghdad discovered a cache of a dozen empty chemical warheads of the same specification that were not listed in a December weapons declaration Iraq pledged was complete and accurate.

Blix said Iraqi officials insisted the 16 empty warheads were "isolated, overlooked items," but that they said they would scour the country for other such devices, which Iraq is prohibited from possessing under various U.N. Security Council resolutions mandating the nation's disarmament.

"They said they were surprised by what they had found, and they said they wanted to make sure they found all of them in the country," he said. "We look forward to that."

He said Iraqi officials also provided him with three documents that U.N. inspectors had requested more than four years ago. He did not describe the contents or the size of the documents.

Although Blix said he regards the disclosure of the warheads and the handing over of the documents as positive steps toward improving cooperation, he warned that Iraq still needs to make fundamental changes in the way it is dealing with the inspections process. He said he pressed Iraqi officials to turn over more information related to past weapons programs, encourage scientists to consent to private interviews with inspectors and allow high-altitude U-2 surveillance aircraft to fly over the country.

"We do not think that war is inevitable," Blix said as he arrived here with Mohamed ElBaradei, director of the International Atomic Energy Agency, the U.N.-chartered nuclear watchdog. "We think that the inspection process that we are conducting is the peaceful alternative."

But he said the process "requires a very active Iraqi cooperation."

Blix, director of the U.N. Monitoring, Verification and Inspection Commission, is scheduled to present a progress report with ElBaradei on Iraq's compliance with the inspections to the U.N. Security Council on Jan. 27. U.N. officials said Blix and ElBaradei today told senior Iraqi officials, including Foreign Minister Naji Sabri and presidential science adviser Gen. Amir Saadi, that Iraq's receptiveness to their demands would influence the tenor of the report.

After the meeting, ElBaradei said he felt that he and Blix were "making some progress."

At present, U.N. officials said, the report probably will acknowledge that inspectors have not found conclusive evidence that Iraq possesses weapons of mass destruction, but it will upbraid Iraq for failing to fully cooperate with the inspectors and will raise questions about information Iraq has refused to disclose.

The report almost certainly will play a crucial role in determining whether Security Council members decide to pass a resolution authorizing the use of military force to topple Hussein and disarm Iraq. A report critical of Iraq also could be seized upon by the Bush administration, which has deployed tens of thousands of troops to the Persian Gulf region, as a justification for unilateral military action on the grounds that the resolution that authorized the inspections calls for "serious consequences" if Iraq fails to comply.

"The message Hans Blix and I are trying to convey as forcefully as possible is that time is running out," ElBaradei said in an interview. "We need to see quick progress on as many of the issues as possible."

For Blix and ElBaradei, the two most important issues appear to be the hand-over of more documents and interviews with scientists.

The two men, who contend that Iraq's 12,000-page weapons declaration is riddled with omissions, have pressed Iraqi officials to provide a fuller accounting of past and current weapons programs, particularly evidence to support Iraq's claims that its stockpiles of chemical and biological weapons have been destroyed. U.S. and U.N. officials have long been skeptical of Iraq's assertion and have insisted on seeing proof that Iraq eliminated tons of bacteriological and nerve agents it covertly produced and weaponized in the 1980s.

Although Iraq has insisted that it has turned over all relevant documents, the discovery last week of about 3,000 pages of material related to uranium enrichment in the home of a physicist has added to concerns that Iraq may be holding back information.

"We told them, 'Do not adopt a legalistic approach. You know what is expected of you,' " ElBaradei said. Blix said the discovery of the documents likely will lead to further inspections of private homes and efforts to question scientists.

The inspectors want to be able to interview Iraqi scientists in private, away from government minders who, the inspectors fear, might discourage the scientists from speaking freely. Although Iraqi officials have said the country's scientists are free to choose how they want to be questioned, U.N. officials contend that the Iraqi government has not done enough to encourage the scientists to talk and instead has effectively dissuaded them from consenting to private interviews.

Over the past few days, the inspectors have asked the government to arrange private interviews with six scientists, but all have said they would not speak without Iraqi officials present.

"If you have nothing to hide, you should tell your people to go and tell your story without any form of intimidation," ElBaradei said.

Iraqi officials bristle at suggestions that they have not been cooperative enough with the inspectors. They note that the inspectors have not been turned away from any sites -- a claim with which the inspectors concur -- and they contend they are following the wording of the resolution on the issue of interviews.

"We have opened all of our laboratories and our military bases and everywhere else the inspectors want to search. We are allowing the inspectors to interview whoever they want," a senior Iraqi official said today. "We're doing everything they asked us to do."

But ElBaradei said Iraq needs "to have a change of heart. They have to be seen not as a country dragged to comply but eager to comply."

Also today, the U.S. Central Command said warplanes participating in a U.S.-British coalition to enforce a "no-fly" zone over southern Iraq struck eight unmanned Iraqi communications relay stations.

IAEA head Mohamed ElBaradei, right, said he and chief inspector Hans Blix were "making some progress" with Iraq.