On Thursday, he said that in effect that moment had come. “For as long as such arbitrary acts and oppression of foreign forces continue, the security agreement with the United States will not be signed,” he said.

The loya jirga overwhelmingly approved the security agreement last week and called on Mr. Karzai to sign it quickly. The Americans have said that would be necessary to allow time to prepare for a longer-term mission.

Mr. Karzai said he was adding a series of new conditions beyond what he had already negotiated and would not sign until those were satisfied. One of those new conditions was an immediate ban on any raids on Afghan homes. While the raids he was speaking of were primarily those carried out by Special Operations forces on the ground, his statement on Thursday made it clear that he now included drone strikes in his prohibition.

The coalition spokesman confirmed that two drone incidents had taken place in Helmand Province on Thursday. The first, in the Garmsir district, targeted an insurgent commander traveling on a motorcycle, but missed him and apparently hit civilians. One child was reported killed, and two women were severely wounded. The targeted man fled on foot and was killed by a later drone strike. In the second, in the Nawa Barak Sai district nearby, another drone strike killed a single insurgent target and caused no civilian casualties, the spokesman said.

“Neither of the strikes were directed at a house or hit a house,” he said. The civilian victims were apparently nearby on the road where the first attack took place. The drones were military, but in keeping with its standard practice, the coalition did not identify which country they belonged to. Both the United States and Britain are believed to have drones operating in Helmand Province.