SANGIN, Afghanistan — A senior British commander in southern Afghanistan said in recent weeks that he had asked that American Special Forces leave his area of operations because the high level of civilian casualties they had caused was making it difficult to win over local people.

Other British officers here in Helmand Province, speaking on condition of anonymity, criticized American Special Forces for causing most of the civilian deaths and injuries in their area. They also expressed concerns that the Americans’ extensive use of air power was turning the people against the foreign presence as British forces were trying to solidify recent gains against the Taliban.

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

A precise tally of civilian deaths is difficult to pin down, but one reliable count puts the number killed in Helmand this year at close to 300 civilians, the vast majority of them caused by foreign and Afghan forces, rather than the Taliban.