Washington: A member of a new Syrian force trained by the U.S. military was believed to have been killed in clashes last week with al Qaeda`s Syria wing, in what would be the fledgling force`s first battlefield casualty, U.S. officials told Reuters on Monday.
The U.S. officials, who spoke on condition of anonymity to discuss the incident, said the Syrian rebel was killed during fighting on Friday with suspected members of Nusra Front.
The Pentagon declined to comment, citing "operational security reasons."
Friday`s incident triggered the first U.S. air strikes to support the Syrian force. At the time, the U.S. military said the fighters repelled the attack, without citing casualties among the U.S.-trained force.
The U.S. military launched its programme in May to train up to 5,400 fighters a year in what was seen as a test of Obama`s strategy of getting local partners to combat extremists and keep U.S. troops off the front lines.
The training programme has been challenged from the start, with many candidates being declared ineligible and some even dropping out. Obama`s requirement that they target militants from Islamic State has sidelined huge segments of the Syrian opposition focussed instead on battling Syrian government forces.
Only around 60 have been deployed to the battlefield so far.
The past week has illustrated that, in Syria`s messy civil war, Islamic State is only one of the threats to the U.S. recruits.
The suspected militants from Nusra Front attacked U.S.-trained fighters on Friday at a compound in Syria, which was also being used by members of a Western-aligned insurgent group, known as Division 30, officials said.
The U.S. officials who disclosed the death of the U.S.-trained Syrian fighter said Division 30 also suffered casualties.
Defending the U.S.-trained fighters could become a growing job for United States, which has been waging daily air strikes at Islamic State targets in Syria.
U.S. officials disclosed to Reuters on Sunday that the United States has decided to allow air strikes to help repel any attack against the U.S.-trained Syrian rebels, even if the enemies come from forces loyal to Syrian President Bashar al-Assad.
U.S. officials have long played down the idea that Assad`s forces - which have not fired on U.S.-led coalition aircraft bombing Islamic State targets in Syria - would turn their sights on the U.S.-backed Syrian rebels.