Iraqi President Saddam Hussein is actively developing weapons of mass destruction, a former chief United Nations weapons inspector has warned.

Richard Butler told a US Senate committee that Iraq had stepped up the production of chemical and biological weapons since UN inspections ended four years ago - and might even be close to developing a nuclear bomb.

Butler: "Current US policy a failure"

However, he added that there was no evidence the technology had been passed to non-Iraqi terrorist groups.

Mr Butler was giving evidence on the opening day of the Senate Foreign Relations Committee hearing, which is meeting to assess the Iraqi threat.

It comes amid growing speculation that the Bush administration is planning a military offensive against Iraq.

One of Washington's closest allies in the Middle East, King Abdullah of Jordan, is due to meet President George W Bush on Thursday - and is expected to urge him not to attack Iraq.

Mr Butler, who led the UN weapons inspectors in Iraq until they were barred from the country in 1998, said that the current US policy of containing the Iraqi president had failed to stop his weapons programme.

Saddam Hussein: Survived in office despite defeat in the 1991 Gulf War

He said, however, that it was still possible that the Iraqi leader might respond to pressure and let arms teams back into Iraq.

"If you can get Russia and France to work seriously with us in Baghdad to make very clear to the Iraqis that this is it, you do some serious arms control or you are toast, then we might have a chance," he said.

But Iraqi nuclear physicist Khidhir Hamza, who defected in 1994, disagreed.

He told the hearing it was "difficult to see how any measure short of a regime change will be effective".

The committee was warned not to underestimate the strength of the Iraqi military.

"It is very dangerous to make quick, sweeping generalisation of the military capability of Iraq," said Middle East expert Anthony Cordesman.

"The fact is - the time lines move toward more and more risk," he said.

Warnings

The committee chairman, Senator Joseph Biden, said that if President Bush was going to send hundreds of thousands of Americans into battle, it was important to do so with the consent of the American people.

He said he would not call administration officials to testify this time, because he did not want to interfere with internal discussions over what to do about Iraq.

Some senators cautioned against attacking Iraq without a clear plan of what to do afterwards.

"It would be a tragedy if we removed a tyrant in Iraq, only to leave chaos," said Mr Biden.

The committee was also warned against antagonising America's allies.

The US could not depend on the same coalition of support which existed in 1991, when the US repelled Iraq from Kuwait, said Senator Richard Lugar.

One of the most outspoken senators, John Kerry of Massachusetts, warned that the Bush administration was being dismissive of friends and allies it might well need later on.