"We have some information that indicates some of these weapons have been given to them," said the official, who spoke on condition of anoymity.

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

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

US officials have said that a US decision to launch military action against 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 coalition forces in Kuwait, increasing the threat of an Iraqi attack before US and British troops have been given the order to move.

"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 covert campaign to encourage Iraqi units to defect or stand aside in the event of war.

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 a clear ultimatum to Saddam Hussein to leave Iraq to avert war in an address to the US public Monday night in what Secretary of State Colin Powell called "the moment of truth."

"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, the point of a US invasion spear that will be backed up by more than 250,000 US forces at air bases in the region and on warships in the Mediterranean, the Red Sea and the Gulf.

US commanders have long anticipated a "rolling start" with more forces arriving after the fighting begins with a brief but violent 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 so far 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. In all as many as 15 warship were being moved to the Red Sea where they would have a clear shot at Iraq over Saudi Arabia with Tomahawk cruise missiles.

Two aircraft carriers -- the USS Theodore Roosevelt and the USS Harry Truman -- remain in the eastern Mediterranean but without Turkish overflight rights they would have to go through Israel and Jordan to reach Iraq.

The United States also has three aircraft carrier battle groups in the Gulf, each with at least 50 attack aircraft. Between 600 and 700 combat aircraft are now deployed throughout the region, according to defense officials.

US warplanes are flying hundreds of sorties a day in the south, including in Iraq.

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