The New York Times quoted Pentagon officials as saying strategy had changed in recent months, shifting towards increased use of ground forces to hunt down remaining fighters.

But the paper said a continuing reliance on air power still often had tragic consequences.

Confusion still surrounds a bombing raid earlier this month in Uruzgan province, which killed up to 46 civilians, 22 of whom were said to have been attending a wedding party.

US officials have given contradictory accounts of events which led up to the attack, and Afghans are angry that innocent civilians appear to have died.

Afghan anger

Afghanistan's Foreign Minister Abdullah Abdullah, quoted by the New York Times, demanded a greater say in the way the US campaign was being conducted.

"If things do not improve, well, I will certainly pray for the Americans and wish them success, but I will no longer be able to take part in this," he was quoted as saying.

Nevertheless, President Karzai's spokesman, Tayeb Jawad, told the BBC that the administration's estimate of less than 500 killed was not that high, considering the scope of the military campaign.

He admitted, however, that a reliance on air strikes rather than riskier ground operations may have played a part in the civilian deaths.

In January, a US academic released a study saying the number of Afghan civilians killed by US bombs had already surpassed the death toll of the 11 September attacks on New York and Washington.

Professor Marc Herold of the University of New Hampshire said his research of news agencies, major newspapers and first hand accounts had yielded a death toll of almost 4,000 people.

Even in January, he described the estimated as "very, very conservative".