KABUL, Afghanistan — In a stark warning to American forces, the Afghan government said it will try to regulate the presence of American troops and their use of airstrikes, while the United Nations yesterday announced that “convincing evidence” exists that an American-led operation killed 90 civilians.

The U.N. sent in a team of investigators, who relied solely on villagers’ statements in alleging the American-led operation in the western province of Herat on Friday killed 60 children and 30 adults. The American military stood by its account, that 25 militants and five civilians were killed in the operation.

“I don’t have any information that would suggest that our military commanders in Afghanistan don’t believe, still, that this was a legitimate strike on a Taliban target,” a spokesman from the defense department, Bryan Whitman, said in Washington.

The U.N. allegation comes a day after President Karzai’s government said it will try to put more controls on the way American and NATO troops operate, a response to a series of airstrikes and other operations this summer that have caused the deaths of scores of civilians.

Afghanistan’s Council of Ministers ordered the ministries of defense and foreign affairs to open negotiations with America and NATO over the use of airstrikes, house searches and the detentions of Afghan civilians. It also called for a “status of force” agreement to regulate the troops’ presence.

Afghanistan’s effort to rein in foreign forces is similar to steps taken by the Iraqi government, which has demanded a timetable for the withdrawal of American troops and greater control of American operations until their departure.

The U.N.’s allegation of such a large number of civilian deaths could set America, the U.N., and the Afghan government on a collision course over the use of military force in Afghan villages, where international troops battle Taliban and Al Qaeda militants daily.

Russia yesterday circulated a draft Security Council press statement expressing serious concern about the numerous civilian casualties reportedly caused by the airstrike and saying member nations “strongly deplore the fact that this is not the first incident of this kind.”

Also yesterday, the U.N.’s anti-drug office reported opium poppy production in Afghanistan was down 19% this year compared to 2007 due to successful campaigns in the north and east though fields in the south remain awash in the heroin-producing crop.

Efforts to eradicate opium poppy fields in the south failed miserably, and the Taliban stand to earn tens of millions of dollars from the trade.