Iraq has given the United Nations the names of more than 500 scientists connected to its arms programme, the UN has said.

The move fulfils one of the demands of last month's UN Security Council Resolution, which required Iraq to provide the names by the end of December.

The enemy will be taught an unforgettable lesson if it tries to attack Mohammed Mehdi Saleh, Iraqi trade minister

Hours earlier, US President George W Bush said Iraq posed a "catastrophic danger" and warned that war could be avoided if Baghdad disposed of its illegal arms.

Washington has stepped up its preparations for a possible military offensive, ordering thousands more troops and dozens of fighter aircraft to go to the Gulf region in the coming weeks.

Spotlight on scientists

At a news conference in Baghdad on Saturday, UN spokesman Hiro Ueki said Iraq had presented a list of "personnel associated with Iraq's chemical, biological, nuclear and ballistic weapons programmes".

The UN said Dr Mijbil had provided useful information

UN arms experts have begun interviewing Iraqi scientists to try to glean information about whether Iraq is pursuing any illegal weapons programmes.

On Friday, weapons inspectors said one scientist had provided useful information indicating Iraq might be trying to develop nuclear weapons - an assertion the scientist, Dr Kazem Mijbil, vigorously denied.

Mr Ueki sought to clarify his remarks, saying his earlier statement did "not make a judgement" that Iraq had a secret nuclear weapons programme.

He acknowledged that Dr Mijbil "was not involved in Iraq's past nuclear programme," although "his statement about non-classified information was of interest to the Agency."

UN arms experts entered their second month of inspections in Iraq on Saturday, visiting at least five sites around Baghdad.

'Burden' on Saddam

In his weekly radio address, President Bush said the "burden" was on Iraqi President Saddam Hussein to destroy his weapons of mass destruction.

"If he refuses, then for the sake of peace, the United States will lead a coalition to disarm the Iraqi regime and free the Iraqi people," said Mr Bush.

The president linked the war on international terrorism to the threat posed by Iraq.

He said the fight "requires us to confront the danger of catastrophic violence posed by Iraq and its weapons of mass destruction".

Troops boost

US Defence Secretary Donald Rumsfeld has signed an order to move thousands more ground forces and combat aircraft to friendly Gulf countries.

US MILITARY BUILD-UP

1,000 US troops due in Israel for an exercise to test Patriot missile defence system 3,000 US army troops end large-scale manoeuvres in the Kuwaiti desert USS Constellation and USS Harry Truman battle groups deployed in Gulf and the Mediterranean in mid-December

Click for more on US deployments in the region

He has also put two more US aircraft carrier battle groups on alert that they could be sent to the Gulf with 96 hours' notice.

The USS Constellation and the USS Harry S Truman, are already in the Gulf and the Mediterranean.

Officials said the order would involve the most visible build-up of forces to date, the Washington Post newspaper reported.

There are currently about 60,000 US troops and 400 aircraft in the region.

"[The order] involves forces that can pretty much deal with anything," an unnamed official told Reuters news agency.

Iraq warned on Saturday that any attempt to invade it would be defeated.

"The enemy will be taught an unforgettable lesson if it tries to attack," said Iraqi Trade Minister Mohammed Mehdi Saleh.