Iraq Isn’t Telling All, U.N. Team Says : Nuclear threat: Just-returned inspectors also say Baghdad may still be hiding sensitive weapons-related materials.

U.N. inspectors who have just returned from Iraq said it appears “probable” that President Saddam Hussein has not disclosed the full extent of work on a relatively modern process to enrich uranium and that the Baghdad government may still be hiding sensitive nuclear materials, it was learned Friday.

In its official report, the 37-member team from the International Atomic Energy Agency said that through imports and local production, Iraq has accumulated a large inventory of natural uranium.

In its report to the agency, obtained by The Times, the team warned that it appears probable that “the full extent” of Iraq’s work on a relatively sophisticated method of enriching uranium--the gas-centrifuge manufacturing process--”has yet to be revealed.” Enriching uranium is a key step in making nuclear weapons.

The team said it identified a number of tasks for later inspection missions to perform, among them to verify the extent of the centrifuge enrichment program. The report would not “exclude the possibility that there are still undeclared locations with sensitive equipment or material installed, in use or stored.”

The inspection team--the third to enter Iraq since the end of the Persian Gulf War--told the United Nations that on the last day of its visit, Iraqi officials turned over data indicating that “some promising results were recently achieved” in research in gas-centrifuge technology.

Team members said that Iraq is developing its own centrifuge technology but that it is dependent on foreign suppliers for key components.

The inspectors said that at one nuclear facility they visited, a layer of concrete was poured over key equipment to conceal it. After the team asked that the concrete be removed, the U.N. scientists were able to confirm that the installation was designed for nuclear enrichment.

The report said Iraqi officials tried to conceal the true identity of a second enrichment facility by telling inspectors that the factory was built for the plastic coating of equipment.

The inspectors added that all “telltale equipment” at three nuclear sites had been removed and turned over to the Iraqi army for destruction and concealment. The team indicated that the destruction of key parts could be designed to hinder a complete evaluation of the scope of Iraq’s nuclear weapons program.

“The army proceeded to transport the equipment to remote locations where much of it was destroyed and buried,” the report said. “ . . . Much of the equipment was destroyed to the point where it was no longer recognizable.”

Under pressure from the United Nations, the Hussein regime has reluctantly provided information about its program of enriching uranium through electromagnetic isotope separation using equipment called calutrons. This technique, much older than using high-speed gas centrifuges, was used in the closing days of World War II to manufacture atomic bombs.

The report was submitted to the IAEA after Iraq failed Thursday to comply with a deadline set by the five permanent members of the U.N. Security Council to present its final list of weapons of mass destruction and an inventory of its nuclear program. It underscored the need for still more U.N. investigations to test Iraq’s cooperation.

In the opinion of both the United States and Britain, the degree of Iraq’s openness with nuclear inspectors could play a key role in the question of when the Security Council decides to allow any sale of oil by Iraq for humanitarian purposes. Iraq has been under a U.N. economic embargo since it invaded Kuwait last August.

The fourth team of inspectors from the IAEA is due in Baghdad today, and Thursday’s report served as a road map of the tasks still to be accomplished by the inspectors.

Iraq’s foreign minister accused the IAEA on Friday of seeking to set the stage for new air strikes against his nation.

Ahmed Hussein Khudayer, in a letter to U.N. Secretary General Javier Perez de Cuellar, charged that the attitude of the atomic energy agency is designed “to prepare for a new military aggression” against Iraq after destroying its nuclear program.

Under the terms of the Security Council resolution ending the war, agreed to by the Baghdad regime, all of Iraq’s weapons of mass destruction--nuclear, biological and chemical weapons and missiles--must be eliminated. Talks are under way among Security Council members to decide on the mechanism under which Iraq would pay a large share of the cost of rendering the weapons harmless.

In an interview from Vienna, Hans Blix, director general of the IAEA, underscored the third team’s report.

“There is no plausible peaceful explanation of what they (the Iraqis) have been doing,” Blix said on NBC’s “Today” program.

Blix said the fourth team was sent to Baghdad with instructions to gain more information on the extent to which the advanced centrifuge technology is being used to supplement the older method.

“In particular, we cannot be sure that the information they gave of having enriched about half a kilogram of uranium . . . is full disclosure,” he said.

“But I can say if a country has mastered the technique of enriching uranium, it’s only a matter of time before they can make a bomb,” Blix added, “and Iraq has mastered that technique.”

When Iraq failed to meet the Thursday deadline for a weapons inventory, the Bush Administration accused President Hussein of playing a “shell game” with his nuclear equipment. U.S. officials stressed, however, that the deadline was not a date for certain military retaliation.

The team’s report on its July 7-18 trip was quite detailed and contained a map of sites that were seen. It said the inspectors visited two sites for electromagnetic isotope separation, at Mosul and at Tuwaitha. Both sites were badly damaged by allied air raids.

Team members reported that the top official of Iraq’s uranium-enrichment program denied that any political decision had been made to use the program to develop nuclear weapons.

“The primary aims were stated to be the development of the country’s technological and industrial infrastructure and the production of fuel for research reactors and a future nuclear power program,” the report said.

But the team noted that the technology it found “suggests a specific intention to produce highly enriched uranium.”