The climactic battle for Baghdad looms closer as US forces advanced in fierce fighting to the Iraqi capital's outer defences yesterday, some 30 miles from the city centre, writes Deaglán de Bréadún, in Doha
They were backed by waves of attacks from coalition aircraft.
US forward units were as close as 19 miles to the outskirts of the city, according to one report.
Commanders of the US 3rd Infantry Division had expected a day-long battle to seize the perimeter of Karbala, 70 miles south of Baghdad - the operation lasted three hours.
Rather than tackling Iraqi soldiers inside, US soldiers secured all major exit routes and continued the drive north.
Up to 15,000 US troops have massed around Karbala waiting to pour across the Euphrates, the last major natural obstacle standing between them and Baghdad on the south-western approach to the capital.
On the eastern flank of the advance, US marines said they had taken control of the main Highway 6 from Kut to Baghdad, and seized a Tigris river crossing described by one senior officer as the "last big bridge" needed for an advance on the Iraqi capital.
Although an Iraqi spokesman dismissed US claims as illusory, it is clear the war is at the beginning of its most critical stage. However, US forces may still await reinforcements before taking final steps to overcome resistance in Baghdad.
Also in central Iraq, helicopters and fighter planes strafed Fedayeen militia active in Najaf, a Shia Muslim holy city.
The Iraqi Information Minister, Mr Mohammed Aaeed al-Sahaf, said Iraqi forces had fought off a US attack on Najaf, and accused the US of bombing shrines there.
However, a US spokesman accused Iraqi forces in Najaf of firing from the gold-domed shrine of Ali, one of the holiest sites for Shia Muslims. He said Americans did not return fire.
There was a cautionary note from the commander of British forces in Iraq, Air Marshall Brian Burridge, who said the decisive phase of the war had begun, but that it might not end soon.
"Decisive phases often take time. We need to proceed with great delicacy in Baghdad, as we did in Basra, because we don't want to cause any more damage to the place than is necessary, and we certainly don't want to add to civilian casualties."
A statement read on behalf of Iraq's President Saddam Hussein yesterday repeatedly called upon the Iraqi people to rise up against the coalition armies.
Observers said it was unusual for the Iraqi leader to make a direct appeal to the people rather than emphasising the role of the armed forces, and that this might reflect increasing military pressure on the regime.
A senior US military spokesman, Brig Gen Vincent Brooks, said in Doha: "The dagger is clearly pointed at the heart of the Baghdad regime."
He told a news conference at US Central Command headquarters in the capital of Qatar that military advances had taken some US troops across a "red line" around Baghdad which could result in a poison-gas attack by Iraqi forces.
"If it's used, we'll be prepared for it being used," he said.
"It causes us to maintain protective postures of our forces as they approach this area, but it doesn't make us stop."
He said US troops had destroyed the Baghdad Division of the elite Republican Guard near the town of Kut, 105 miles south-east of Baghdad, and had fought two other Guard divisions.
The US offensive followed days of heavy bombardment of the Republican Guard's Medina, Baghdad, Hammurabi and Al Nida divisions.
Bombs struck central Baghdad, reportedly killing several motorists and hitting a Red Crescent hospital. At least five cars were said to have been crushed, with their drivers burned to death inside.
Mr al-Sahaf said air assaults had killed 24 civilians and wounded 186 in the previous 24 hours, with 10 dead and 90 wounded in Baghdad.