He heaved and dry vomited, paced, then sat silently, filled with rage, knowing the sniper had violated a ceasefire brokered between the US-led Coalition Provisional Authority, Iraq's interim Governing Council and Fallujah city elders.

The pain and gut-wrenching agony of watching fellow marines fall in action has taken its toll over a back-breaking week of street-to-street fighting in the stronghold of the anti-US insurgency.

Rank and file marines feared the truce would rob them of victory. It would leave them with friends dead and insurgents running free after the troops entered Fallujah last Monday, intent on breaking the backs of the resistance.

"There are still criminals and terrorists out there. We haven't finished clearing the city," said Lieutenant Matthew Agnoli Sunday morning.

Just minutes later a panicked voice broke out on his military radio, announcing that two marines had been shot.

The two casualties were rushed out of the city but their fellow marines ran back to the abandoned garage they have converted into a command post, drenched in sweat, panting, with some of their uniforms stained in blood.

Anything short of the surrender of rebels would be seen as a defeat for the marines, particularly if US forces eventually left the city and transferred security responsibility to the police, Agnoli feared.

"It would make things 10 times worse. It would give them the sense they were victorious, that they pushed out the US marines, and boost their morale and increase their will to fight," said Agnoli.

On Sunday, many people had bloodshot eyes and were tired.

They had come perilously close to dying this past week. Some spoke of a marine climbing a ladder only to find a sniper look down on him and shoot him dead.

A mortar crashed into a humvee and sent shrapnel flying into one marine's arm and another's head.

At the very least, marines wanted to see the handing over of the masterminds of the murder of four US contractors in the heart of Fallujah on March 31 that triggered this offensive.

"I don't see how we can leave the city unless they give us the men who killed the four Americans or some high priority people," said Lance Corporal Jeff Starr. "Then I consider it a success. If they don't, the rebels will think they fought the marines out of Fallujah."

Most of them feared the rebels would flee to fight another day and continue prey on them with rocket ambushes and roadside bombs as they have done since the fall of Baghdad last year.

"I don't think the ceasefire is going to work," said Staff Sergeant Rocky Kinzer, hours after his fellow marines were struck down by the sniper in a wasteland of abandoned metal shops, wild dogs and rusting truck cabs left to rot in the street.

"Things have been this way so long. They'll leave the city and go fight us in another place."

WAR.WIRE