"We've seen that the Medina and Baghdad divisions are no longer credible forces," Major General Stanley McChrystal, the vice director of operations of the Joint Staff, said in Washington.

The Republican Guard, which is believed to have eight divisions at a combined strength of 60,000 men, is considered the best trained and most motivated of Iraq's armed forces and key to any final defense of the capital against US-led forces seeking to topple Saddam Hussein's regime.

Earlier at the US Central Command base here, US Brigadier General Vincent Brooks announced that the Baghdad division "has been destroyed."

"The First Marine Expeditionary Force attacked the Baghdad division near the town of Al-Kut and has crossed the Tigris River," Brooks said. Al-Kut is about 150 kilometers (90 miles) southeast of the Iraqi capital.

"We will approach Baghdad. The dagger is clearly pointed at the heart of the regime and will remain pointed at it until the regime is gone," he told a news conference.

"The dagger remains firmly in our grasp and under good control. When it's time to be applied further, it will be applied further."

But in Baghdad, an Iraqi military spokesman denied the Baghdad division had been destroyed.

"These allegations have no foundation and are part of the hostile campaign against Iraq," the spokesman told AFP.

"To the contrary, the Baghdad division maintains its cohesion and has a morale of steel. It has not suffered any losses and is ready to confront the enemy and destroy it," he said.

Later, the Baghdad division's commander told Iraqi television 17 members of the unit had been killed and 35 wounded.

"The command is intact and we are ready to confront the enemy wherever he may be," said the general, whose name was not specified.

"We're prepared to defend our homeland and its leadership and God willing, we will inflict on the enemy a lesson he will never forget," the general said.

A statement by Saddam quoted by state television said Iraqi troops would defeat the invasion forces.

"Many thousands of soldiers are defending the homeland ... and they will not allow them (allied forces) to go into Baghdad without defeating and repelling them," Saddam said in response to a message of support from one of his nieces, the television said.

Besides the Baghdad and Medina divisions, US Central Command also said earlier Wednesday that coalition troops were battling the Nebuchadnezzar division and targetting the Adnan division to the north with airstrikes.

Marines cut off the Baghdad division during a major battle on the approach to Al-Kut after crossing the Tigris, a senior officer told AFP on the ground.

"The final push to Baghdad is now on," he said.

"The Baghdad division of the Republican Guard is irrelevant. The 3rd and 4th divisions of the Iraqi army are in the bag."

The Republican Guard was set up by Saddam and is headed by the Iraqi leader's son Qusay.

It grew in strength throughout the bloody war with Iran from 1980 to 1988, at its peak the ranks swelling to 150,000 men and emerging as a reliable alternative to an increasingly deficient regular army.

The Republican Guard also led the August 1990 invasion of Kuwait, but took a beating in the subsequent Gulf war in 1991.

Considered fiercely loyal to Saddam, the Guard is made up almost exclusively of the president's Sunni Muslim Arab minority rather than Kurds or Shiite Muslims.

Russian-made T-72 tanks and a dense anti-aircraft defense system are the key weapons at the Guards' disposal.

SPACE.WIRE