Three US servicemen were killed by a roadside improvised explosive device in Afghanistan on Tuesday, the Nato-led Operation Resolute Support said in a statement.
Three more servicemen and one US contractor were wounded in the blast near the central province of Ghazni, which has been under heavy siege from the Taliban in recent months.
The Nato statement gave no details but Mohammad Arif Noori, a spokesman for the provincial governor, said an armoured vehicle carrying US troops hit a large roadside bomb in Shahbaz area, just outside the city on Tuesday morning.
Thousands of civilians, mainly Shi'ite Hazaras, have fled their homes in Ghazni as the Taliban pressed further into once-safe districts.
Parliamentary elections were delayed in Ghazni following disputes over representation between different ethnic groups.
In August, the Taliban briefly overrun the provincial capital, Ghazni city, before they were pushed back by US air strikes.
The city sits on a strategic position between the Afghan capital Kabul and Kandahar in the south.
The deaths are the latest in a growing toll on US forces in Afghanistan following the death of an army Ranger during an operation against Al Qaeda militants in Nimruz province on Saturday. Resolute Support said the soldier had been accidentally shot by a member of Afghan partner forces.
The US has been attempting to bring the Taliban to the negotiating table to end the 15-year-long war, which started after the United States invaded Afghanistan in 2003.
At least 11 US service members and four Czech soldiers serving with Resolute Support have been killed this year, either in combat or so-called "insider attacks" by Afghan soldiers or the police.
The US is leading the Nato Operation Resolute Support, which provides counterterrorism assistance and air support to the internationally recognised Afghan government. About 14,000 US troops are stationed in the country, fighting the Taliban, Al Qaeda and ISIS.
This month, the Taliban held talks with US officials in Qatar, but no agreement was reached on "any issue".
Afghanistan is due to have presidential elections in April, but this might be delayed to July as officials are struggling to tally votes from parliamentary elections in October.