"I never believed that we'd just tumble over weapons of mass destruction in that country," Defense Secretary Donald Rumsfeld told "Fox News Sunday."

The United States led a war to depose Iraqi president Saddam Hussein, saying he had hidden banned weapons from UN inspectors.

"Saddam Hussein and his entire regime learned to live with UN inspections," Rumsfeld said.

"The intelligence shows that they were systematically trying to prevent the inspectors from finding them."

Rumsfeld said Iraqi prisoners would help US forces find the weapons of mass destruction.

"We're going to find what we find as a result of talking to people, I believe, not simply by going to some site and hoping to discover it," he said.

Asked if senior Iraqi officials now in US custody were providing information on chemical, biological or nuclear weapons, Rumsfeld said lower-ranking officials would likely provide the most interesting leads.

"We're going to have to find people not at the very senior level, who are vulnerable, obviously, if they're in custody, but it will be people down below who had been involved in one way or another."

Secretary of State Colin Powell said so far, US forces have not found any nuclear weapons in Iraq but that "we will find weapons of mass destruction."

"We haven't found any evidence of nuclear weapons in Iraq as a result of what we have been able to see thus far," he told NBC's "Meet the Press."

"But a program is more than just a weapon."

"We didn't think he had a weapon. But he kept in place the infrastructure, and he never lost the infrastructure or the brain power assembled in a way to use that infrastructure, if he was ever given a chance to do so," Powell said.

Rumsfeld said he still did not know whether the deposed Iraqi leader was alive.

"If I had to guess, I would suspect that he may very well be alive," he said. "He and his crowd are gone. They're either in a tunnel someplace or in a basement hiding. We'll find them, if he's alive."

According to an article Sunday in The Washington Post, a major radioactive waste repository in Iraq located by a US Defense Department team had been looted and it was unclear whether nuclear materials were missing.

The discovery at the Baghdad Nuclear Research Facility, the second such since the end of the war, revealed heavy plundering that persuaded US officials deadly materials may have been stolen, the Post said.

A survey by a US Special Forces unit and eight nuclear experts from the Pentagon offered evidence suggesting that Iraq's most dangerous technologies had been dispersed by the war, the article said.

None of the seven sites linked with Iraq's nuclear program and visited by the Pentagon's "special nuclear programs" teams since the war ended last month have been found intact.

Meanwhile, The New Yorker magazine said that US insistence that Iraq has such weapons has been based on dubious intelligence from a shadowy Pentagon committee that now dominates US foreign policy.

The Pentagon's Office of Special Plans (OSP) has become President George W. Bush's main intelligence source, particularly over Iraq's weapons of mass destruction and the country's links to al-Qaeda, the magazine reported in its May 12 edition.

But the OSP, the brainchild of US Deputy Defence Secretary Paul Wolfowitz, relied on questionable intelligence from the Iraqi National Congress (INC), the exile group headed by Ahmad Chalabi.

"The INC has a track record of manipulating intelligence because it has an agenda. It's a political unit, not an intelligence agency," a former senior CIA official and Middle East specialist said in the article by Seymour Hersh.

Time magazine also reported that the US military may have played down its use of cluster bombs during the war in Iraq.

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