A US military spokesman denied the request for US forces to leave was made, formally or otherwise, or that they had caused most of the casualties. But the episode underlines differences of opinion among NATO and US military forces in Afghanistan on tactics for fighting Taliban insurgents, and concern among soldiers about the consequences of the number of civilians being killed.

A precise tally of civilian casualties is difficult to pin down, but one reliable count puts the number killed in Helmand this year at about 300, most caused by foreign and Afghan forces rather than the Taliban. "Everyone is concerned about civilian casualties," the senior British commander said. "Of course it is counterproductive if civilians get injured, but we've got to pick up the pack of cards that we have got. Other people have been operating in our area before us." After 18 months of heavy fighting, the British commanders say they are finally making headway in securing key areas such as Sangin and are now in the difficult position of trying to win back support among local people whose lives have been devastated by aerial bombing.

US Special Forces have been active in Helmand since US forces first entered Afghanistan in late 2001 and for several years they maintained a small base outside the town of Gereshk. But the foreign troop presence was never more than a few hundred. British forces arrived last northern spring and now have command of the province with 6000 men deployed, with small units of Estonian and Danish troops. US Special Forces have continued to help in fighting insurgents, operating as advisers to Afghan security forces.

It is these small teams that are coming under criticism. They work in small units that rely on airstrikes for cover because of their inability to defend themselves if they encounter large groups of insurgents. Such teams have often called in airstrikes in Helmand and other places where civilians have subsequently been found to have suffered casualties. In just two cases, airstrikes killed 31 nomads west of Kandahar in November last year and another 57 villagers, half of them women and children, in western Afghanistan in April.

The chief British press officer in Helmand, Colonel Charles Mayo, defended the US Special Forces, saying they were essential to NATO's efforts to clear out heavily entrenched Taliban insurgents. A US military spokesman said Special Forces would continue to operate in Helmand for the foreseeable future. He denied their tactics had increased civilian deaths and blamed the Taliban for fighting from civilian compounds.

For months, frequent reports of civilian casualties have trickled out of Helmand, scene of some of the fiercest battles of the recent war. But there has rarely been independent confirmation of the reports because the province has been too dangerous for journalists to visit. Yet there is no doubt there have been civilian casualties. On a rare visit to Helmand in mid-July, a journalist encountered children who were still suffering wounds sustained in a May bombing raid or another around that time. Their father, Mohammadullah, brought them to the gate of the British army base seeking help.

His son, Bashir Ahmed, 2, listless and stick-thin, seemed near death. The boy and his sister Muzlifa, 7, bore terrible shrapnel scars. NATO doctors had removed shrapnel from the boy's abdomen at the time of the raid and had warned his father that he might not survive, but two months later he was still hanging on. The father said the bombing raid killed six members of the family and wounded five. His wife lost an arm and the children's grandmother was killed.

He said 20 people were killed in the airstrikes. NEW YORK TIMES