WASHINGTON, Sept. 17 (Xinhua) -- The U.S. Defense Department confirmed on Tuesday that a U.S. soldier died in Afghanistan on Monday.

The soldier was killed by small arms fire when his unit was engaged in combat operations in Wardak Province of Afghanistan, said the Pentagon in a statement, adding the incident is currently under investigation.

The United States maintains some 14,000 troops in Afghanistan, which largely provide training missions to local Afghan forces while also conducting counterterrorism operations against terror groups.