At least two U.S. soldiers have been killed in an apparent suicide bombing in northern Syria.
The Islamic State group claimed responsibility for Wednesday's explosion that also killed two other Americans - a defense contractor and defense department employee.
The total death toll is said to be at least 18, with a similar number of others being injured.
The White House said President Trump was briefed on the situation.
Vice President Mike Pence said Washington still intends to withdraw U.S. troops from Syria.
U.S. forces were in the city of Manbij to back Kurdish and Arab fighters who are wiping out the last remaining ISIS fighters in the country.