Commanders said Sunday that 20,000 troops in the 3rd Infantry Division, spearheading the Iraq invasion and concentrated near the Euphrates valley town of Najaf, were preparing a push north in a few days.

But further east near al-Kut, an AFP correspondent said more than 5,000 marines had dug in amid expectations the drive to the capital was still weeks away.

In the north, Iraqi positions near the demarcation line between Kurdish- and Iraq-held trritory came under fire from US and British forces for the third night running early Monday, an AFP correspondent reported.

The bombardments, which were heard in the Kurdish town of Kalak, some 40 kilometres (25 miles) east of the city of Mosul, began shortly after midnight local time (2215 GMT Sunday).

Kurdish forces are now slowly advancing on the northern Baghdad-controlled oil city of Kirkuk.

US troops grouped near Najaf, a Shiite Muslim holy city about 160 kilometers (100 miles) south of Baghdad, were expected to move on the capital within a week, an intelligence officer told AFP.

Meanwhile, coalition warplanes kept pounding Iraqi positions in "shaping up" operations to clear the way for the offensive, the elite Republican Guard, defending the southern approaches to the capital, a particular target.

The Pentagon announced that three marines were killed and one was injured when a UH-1 Huey transport helicopter crashed Sunday in southern Iraq while heading towards an unspecified "forward operating base".

US commander General Tommy Franks, speaking in Qatar, said coalition forces had opened a "solid front" in the Kurdish north and promised another 120,000 US troops would pour into Iraq within weeks, joining the 90,000 who began the ground war.

He shrugged off criticism that US planners had underestimated Iraqi resistance and were rushing to fill the gap.

Franks said their orders had been issued between January and early March, adding: "What that may imply is that the plan you see is in fact the plan we have been on. I can simply assure you that that is the truth."

British troops found a new stash of nuclear, biological and chemical weapons gear near the besieged southern city of Basra, which the coalition says could suggest Saddam may unleash the outlaw weapons he is alleged to have.

Among the items discovered were a Geiger counter, nerve gas simulators marked "dangerous to humans if exposed for ten minutes without a respirator," and chemicals to detect nerve gas.

British commandos also said they captured an Iraqi general and another senior officer in fighting with paramilitaries southeast of Basra.

But their success was offset by news from the Ministry of Defence in London, that a British soldier was killed and several others wounded in fighting around the city.

Close to Basra, and near the village of Imam Anas to the southwest, British forces also found large supplies of arms and ammunition. At least 150,000 rounds of machine gun ammo were destroyed.

An Iraqi army spokesman said more than 4,000 volunteers had come to Baghdad from across the Arab world and were ready to die in suicide bombings against US and British forces.

Radical Palestinian group Islamic Jihad said a first batch of its suicide bombers was in Baghdad.

WAR.WIRE