VIENNA, Austria - A top U.N. weapons hunter says it would have been "virtually impossible" for Iraq to revive a nuclear bomb program with equipment recently dug up from a Baghdad backyard, as the Bush administration contends.

Jacques Baute said the long-term monitoring of Iraq's nuclear establishment planned by the U.N. Security Council would have stifled any attempt to build a huge uranium-enrichment plant for making bomb material.

"This is a mistake people are making," Baute said. Such contentions ignore the fact that Iraq would have operated for years under international controls had the U.N. plan not been aborted by war, he said.

Baute also said in an interview with The Associated Press that it appears the unearthed cache of uranium enrichment parts, surrendered by an Iraqi scientist last month, lacked critical components, and its accompanying blueprints were marred by errors.

Baute, a French nuclear physicist, led the International Atomic Energy Agency inspection teams that - until the U.S.-British invasion in March - crisscrossed Iraq in search of banned weapons.

His assessment of the hidden equipment came as a furor grew in Washington over President Bush's use of an earlier allegation - that Baghdad sought uranium from Niger - to bolster the White House case for war.

It was Baute's investigation last February that unmasked as forgeries the documents that underpinned the claims about Niger.

National Security Adviser Condoleezza Rice is holding to the Niger story, noting that the British government now says other, unspecified intelligence supports the uranium allegation. But London hasn't supplied Washington with any such information, Rice acknowledged.

Likewise, Baute's office has received nothing from the British three weeks after asking for the purported independent evidence, said sources at IAEA headquarters in Vienna, speaking on condition of anonymity.

The U.N. agency's experts believe all reports of a Niger connection stem from the same bogus documents.

Eliminating Iraq's supposed weapons of mass destruction was the main reason given by Bush for invading the Arab country. But three months of searching by the U.S. military has found no banned arms, just as some 700 inspections by U.N. teams from November to March also uncovered no signs of nuclear, chemical or biological weapons programs.

Before the war, Baghdad said all its chemical and biological weapons had been destroyed during U.N. inspections in the 1990s.

However, President Bush said Monday he remained convinced that Saddam Hussein was trying to develop a weapons program that threatened the world and justified the United States going to war. "Our country made the right decision," Bush said.

State Department spokesman Richard Boucher had no comment when asked about Baute's statements. But he told reporters: "I think the findings in Iraq demonstrate that Iraq had not abandoned its intentions on nuclear programs. Just buried them. Maybe more. We'll see. We'll find the full extent of that as time goes on."

Iraq never had nuclear arms but was making progress building sophisticated centrifuges to produce enriched uranium for bombs when the 1991 Gulf War intervened. Inspectors dismantled the program.

In early June, the centrifuge program chief, Mahdi Shukur Obeidi, turned over to U.S. authorities equipment and documents he said he buried in his garden in 1991, when he said Iraqi leaders told him to hold the parts to revive the program.

The IAEA notes that Obeidi's account tends to undercut one White House contention: that Saddam's government had secretly resumed its nuclear program in recent years.

White House press secretary Ari Fleischer has instead now focused on the Obeidi cache's potential, saying it would have allowed Iraq to rebuild weapons facilities "once sanctions were ended."

But Baute, in the interview Friday, pointed out that once U.N. economic sanctions were ended, after inspectors certified Baghdad's weapons work had ceased, the Security Council was to have imposed an Ongoing Monitoring and Verification regime on Iraq - controls short-circuited by the U.S.-British invasion.

Inspectors, with unhindered access under U.N. resolutions, would have kept close watch on Iraq's military-industrial complex, aided by air and water sampling technology, satellite and aerial surveillance, and monitoring of Iraq's imports.

An enrichment plant, a vast array of thousands of centrifuges, would have been easily detected, said Baute, who once helped build French nuclear bombs.

"To have turned it into a full-blown enrichment program while OMV was in place would have been virtually impossible," he said of the Obeidi equipment.

Although U.S. officials have not shared their Obeidi data with the IAEA, Baute's experts closely examined available photos of the components and found they included one critical part, the bottom bearing assembly.

But other vital elements apparently are lacking, Baute said, including the advanced carbon-fiber rotor, the spinning tube in which uranium gas is separated.

"It is far, far from being a complete set," he said.

He also noted the Iraqis would have had to expose themselves by searching for foreign manufacturers to duplicate complex components.

As for Obeidi's documents, they appear to be copies of centrifuge drawings and papers seized by IAEA inspectors in 1995, Baute said.

"These Iraqi drawings seem to contain mistakes," he said. German engineers who secretly assisted the centrifuge program apparently didn't leave their hosts finished designs, and the Iraqis erred at times in filling in gaps.