"We have some information that indicates some of these weapons have been given to them," said one official, who spoke on condition of anoymity. A second US official also said there were signs chemical munitions were being distributed to Iraqi units.

The officials said the weapons were being given to the Republican Guard, which is reputedly the most loyal unit to Iraqi leader Saddam Hussein.

President George W. Bush has accused Saddam Hussein of authorizing military commanders to use chemical weapons, but this was the first indication that such weapons were being given to units.

As diplomatic efforts to end the Iraq crisis came to an end Monday, the Iraqi leader denied having weapons of mass destruction.

The defense official, who said hard evidence was still lacking, was unable to provide details on which Republican Guard units were receiving chemical munitions, or whether the information suggests Iraqi forces may be preparing attacks on US and British forces in Kuwait.

US officials have said a US decision to attack Iraq would be the "moment of maximum danger" of a pre-emptive chemical or biological weapons strike against coalition forces or surrounding countries like Israel or Kuwait.

Iraq last week moved artillery into positions within range of Kuwait, increasing the threat of an Iraqi attack, according to US officials.

"Our guys are certainly prepared for that," said Lieutenant Colonel David Lapan, a Pentagon spokesman.

Senior US officials have publicly warned Iraqi leaders they will face war crimes charges if chemical, biological or nuclear weapons are used, and have conducted a campaign to encourage Iraqi units to defect or stand aside.

US defense officials said they see no other major changes in Iraqi defenses. Iraqi forces have left their garrisons and are dispersed in defensive positions, they said.

Abandoning diplomacy, Bush planned to issue an ultimatum to Saddam Hussein to leave Iraq to avert war in an address to the US public Monday night.

"We're all waiting to see what's next," said Lapan. "We're all primed and ready."

There are now more than 140,000 US troops and another 25,000 British troops in Kuwait, across the border from Iraq. And these are backed up by more than 100,000 at air bases and on warships in the Mediterranean, the Red Sea and the Gulf region.

US commanders have long anticipated a "rolling start" with more forces arriving after fighting begins with an air campaign designed to shake apart the regime in Baghdad, followed closely by a fast-moving ground offensive out of Kuwait.

They face a major complication in the north where they have been denied access to Turkish bases and air space for a northern offensive.

The United States was still holding discussions with the Turks, but said a Pentagon official, "We're focusing on the workarounds now."

"We've told the Turks not to get into a fight with the Kurds, and we've told the Kurds not to get into a fight with the Turks," said another defense official, speaking on condition of anonymity.

Since Friday, at least eight cruise missile-firing US warships, including three submarines and five surface warships, have passed through the Suez Canal from the Mediterranean to the Red Sea, according to US Navy and Egyptian officials. Up to 15 warships were being moved to the Red Sea where they would have a clear shot at Iraq over Saudi Arabia with Tomahawk cruise missiles.

The aircraft carriers USS Theodore Roosevelt and USS Harry Truman remain in the eastern Mediterranean but without Turkish overflight rights planes would have to cross Israel and Jordan to reach Iraq.

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