The Pentagon on Thursday said another six troops were injured in attacks last week in north-eastern Syria, which US officials have blamed on Iranian-backed militants.
Brig Gen Pat Ryder, the Pentagon spokesman, said in each of the two attacks, six soldiers were injured and an American contractor killed, for a total of 14 casualties.
He said four American service members at Hasakah and two at Green Village have been diagnosed with traumatic brain injuries and are being treated at their bases.
Evaluations are continuing on personnel at the bases.
Brig Gen Ryder said at briefing that the US now assesses that eight militants, all associated with Iran’s Islamic Revolutionary Guard Corps, were killed in the American counter-strikes by fighter jets.
The initial strike by militants on March 23 by a small explosive drone set off a series of retaliatory bombings.
The top US commander for the Middle East, Gen Erik Kurilla, quickly warned that the US was prepared to launch more attacks if needed.
The drone attack was followed by two simultaneous strikes against US forces late on March 24. The US retaliated with strikes on two IRGC locations.
Independent reports on the numbers of people killed and wounded in the US strikes varied.