On Sunday, however, American officials said General Allen’s order did not necessarily go that far and sought to describe it in more nuanced terms, saying that NATO would continue to conduct operations against insurgents who use civilian dwellings for shelter.

“When there is concern over the presence of civilians, air-delivered munitions will not be employed while other means are available,” said a senior United States defense official who was not authorized to speak publicly on the policy deliberations.

Militants often hide in civilian homes, so a complete ban on airstrikes could hinder the ability of American forces to pursue the Taliban. General Allen’s order does not affect ground operations against insurgents. An agreement between the two countries in April gave lead authority for night raids to the Afghans, although missions are to be conducted jointly and targets selected by consensus. Allied officials still retain control over dropping bombs in these operations, and Afghan officials say they were not involved in the decision to carry out the fatal airstrike last week.

That attack marked a setback to an encouraging trend: Civilian casualties in Afghanistan dropped significantly in the first four months of 2012, and a smaller proportion of the deaths was attributed to coalition and Afghan forces compared with a year earlier, the United Nations director in the country said last month.

The joint Afghan-NATO raid last week was hunting a Taliban commander and some of his fighters who had holed up in a home in Logar Province where a wedding had taken place, according to local residents. An early-morning firefight broke out between the coalition troops and the insurgents, with the civilians trapped inside. The coalition decided to call in an airstrike, which killed the insurgents but also 18 civilians, including 9 children, Afghan officials said.