KABUL — The United States conducted an airstrike on Wednesday against Taliban fighters in Afghanistan’s southern Helmand province, a U.S. forces spokesman said, the first such attack since a troop withdrawal agreement was signed between the two sides on Saturday.

The Taliban fighters were “were actively attacking an [Afghan National Security Forces] checkpoint. This was a defensive strike to disrupt the attack,” said Colonel Sonny Leggett, a spokesman for the U.S. Forces in Afghanistan in a tweet.

He said Washington was committed to peace but would defend Afghan forces if needed.