Three US service members and a contractor were killed in Afghanistan by an improvised explosive device on Monday, the NATO-led Resolute Support Mission said in a statement.
Three US service members were also wounded in the incident near Bagram air base close to Kabul, the statement said.
It gave no further details.
The latest deaths brings the number of US service members’ deaths in Afghanistan to seven in 2019, and a total of 68 US military deaths since January 2015, according to US government and NATO reports.
Last month two US service members were killed in Afghanistan while conducting an operation.
The war has taken a much larger toll on Afghan security forces and civilians.
Violence has been relentless in Afghanistan even though Taliban militants have held several rounds of talks with US officials about a peace settlement.
The talks began late last year, raising hopes for an end to the conflict. The latest round ended this month with both sides citing progress.
The Resolute Support Mission consists of 17,000 troops, about half of them from the United States. A smaller number of US troops operate in Afghanistan under a counter-terrorism mission.