"We have no reason to believe that these were inaccurate figures," said the occupation forces' deputy director of operations Brigadier General Mark Kimmitt, in response to repeated questions from journalists about the reported death toll.
"We stand by these numbers that were reported by the soldiers involved," he said at a news conference in Baghdad.
Growing doubts have been expressed about the figures in the light of the insistence of the town's hospital that it received just eight bodies, including a child and at least one elderly Iranian woman who were clearly not fighters.
At an earlier briefing on Monday, Kimmitt had suggested that the fighters’ corpses must have been carried away by their comrades.
But his theory raised eyebrows as he also reported 22 fighters were wounded and one captured in what he described as "coordinated" attacks on three separate convoys.
Lieutenant Colonel Ryan Gonsalves, who commands the 166th Armoured Battalion in Samarra, which was involved in Sunday's clashes had only explicitly referred to two groups of 30 ambushers each and another four attackers in a car.
"It is important to understand that many of these questions will never be answered"
Deputy director of operations,
That raised questions about how such a small number of mainly injured survivors carried off so many bodies.
The occupation forces’ chief civilian spokesman in Baghdad Dan Senor leapt to the defence of the US military.
"Our troops go to very great efforts to give us scrupulous reports," he said. "They have been forthright and honest, and will continue to be."
Pressed further, the US general grew increasingly testy. "I trust the reports of my soldiers ... There is no reason to doubt what the soldiers say."
Challenged about the US-led administration’s legal responsibility to inquire into civilian deaths under occupation, Kimmitt replied: "I have spoken to (Major) General (Raymond) Odierno today. We will do a determination of what happened. He is fully committed to finding out the truth."
But he added: "It is important to understand that many of these questions will never be answered."
Asked about the timeframe for the conclusion of the investigation, Kimmitt offered no reply.