The clash occurred on Monday when fighters attacked a joint US-Afghan patrol near a coalition base in insurgency-hit Deh Rawood district in central Uruzgan province, according to Major Richard Sater, based at Bagram air base.
Special operations soldiers were patrolling near the base when they came under small arms fire, he said. "One Afghan militia force soldier was killed during the brief exchange of gunfire," he said.
The Americans claim that no coalition soldiers were hurt during the fighting with several fighters armed with AK-47 and rocket propelled-grenade launchers.
The US military also said it discovered six rockets on Tuesday planned for firing on the Deh Rawood US military base in Shkin, on the border of Pakistan. The US military says that the rockets were destroyed.
Shkin on the border with Pakistan, 220 kilometres south of Kabul, has been dubbed by the US military "the most evil place in Afghanistan," because more US soldiers have been killed there than elsewhere in the country.
In neighbouring Khost province, US-led forces on Tuesday discovered and destroyed a home-made bomb planted on a road frequently used by coalition soldiers, according to the American military.
Similar incidents in the past have been blamed on Taliban fighters and their allies from al-Qaida
Major Richard Sater was unable to say who was behind the Deh Rawood attack but similar incidents in the past have been blamed on Taliban fighters, their allies from al-Qaida, or supporters of the former Afghan premier Gulbuddin Hekmatyar.
Two years after the toppling of the Taliban, remnants of the militia continue to launch frequent attacks on foreign aid workers and troops, mainly along the 2,400 kilometre rugged and porous Afghan-Pakistan border.
The 12,500-strong US-led forces have been hunting Taliban and al-Qaida cells for two years, mostly in the southern and eastern Pashtun-dominated provinces that share the same ethnicity with the Taliban.