Several coalition fighters were wounded by a Russian airstrike against positions held by the Syrian Democratic Forces, a militia backed by the USA -led coalition in the fight against the Islamic State.
Syria is now very crowded as Iranian, Russian and American forces operate within striking distance of Hezbollah, Assad's military, and Syrian rebels among others, which still include a quickly diminishing ISIS. He has been officially designed an "enemy combatant" by the Defense Department.
Brown said the American was taken into custody on or before Tuesday by Syrian Democratic Forces, a US -backed alliance of Kurdish and Arab militia fighters in Syria.
The SDF, half of whose forces are members of the Kurdish People's Protection Units (YPG), are backed by the US-led Global Coalition to Defeat ISIS.
On Thursday, the chief spokesman for the United States military command referred all questions about the news.
Heather Nauert, spokeswoman for the State Department, told reporters earlier Thursday that anyone who goes to fight for ISIS "can't be very bright".
Mohamad Jamal Khweis, 27, was captured by Kurdish forces in northern Iraq in March 2016.
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The away support were still revelling in their lead when the Burnley rearguard switched off and Liverpool levelled through Salah. He goes in between; it was a bouncing ball, they are quicker and they are more used to these situations, they do it more often.
The Russian- and USA -backed offensives against Islamic State in Syria have mostly stayed out of each other's way as the two states seek to avoid conflict, with the Euphrates often acting as a dividing line between them.
He added, however, that as the two groups converge on the Islamic State position from opposite sides, it will get more hard to stay out of each other's way.
Foreign fighters captured in Iraq have been held by the Iraqi military, which has said it would try them.
It is estimated that almost 250 American citizens had joined or attempted to join Isis in Iraq and Syria as of 2015. It is now illegal to try US citizens at military commissions.
The United States and Russian Federation are backing separate offensives in Syria's multi-sided conflict - with both sides advancing against the Islamic State militant group in the eastern region that borders Iraq.
Khweis, due to be sentenced next month, said he had traveled undetected from Fairfax County to join the Islamic State in Syria but at the time of his capture had deserted the militants and was trying to make his way home.