Falluja, Iraq's other main flashpoint and a bastion for Sunni Muslim insurgents, was enjoying a second day of calm.

But five civilians were killed as they tried to escape overnight shelling by US forces in the nearby town of Karma, witnesses said.

The US military said an American soldier had been killed and two wounded when their patrol hit an anti-tank mine near Saddam Hussein's hometown of Tikrit Friday.

Since March 31, at least 94 US soldiers have died in action in Iraq -- more than were killed during the three weeks last year between the invasion of Iraq and the fall of Saddam.

Tension remained high in Najaf, where 2,500 US troops are poised nearby with orders to kill or capture Sadr.

A spokesman for the fiery cleric said on Saturday that negotiations were at a dead end. A US spokesman denied any direct talks had taken place, although he said Iraq's US-led administration was keen to avoid bloodshed in Najaf.

Caught in the face-off between US troops and Sadr's Mehdi Army militia, Najaf residents complained their lives and livelihoods were at risk with shops closed and streets around the city's shrines crowded with gunmen instead of pilgrims.

Sadr's supporters say Iraq's top Shia clerics back the uprising they staged this month against the US-led occupiers.

"We know that any assault from the Americans on the holy city of Najaf will be the zero hour for the revolution all over Iraq," said Sadr's spokesman, Qays al-Khazali. "The religious authority has a clear stand in providing us with moral support."

But representatives of Najaf's four grand ayatollahs have distanced themselves from the junior cleric's actions.