First US-trained Syria Rebel Believed Killed in Fighting: Sources

Washington: A member of a new Syrian force trained by the US 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, US officials said in an interview on Monday.

The US officials, who spoke on condition of anonymity to discuss the incident, said the Syrian rebel was believed to have been killed during fighting on Friday with suspected members of Nusra Front.

One of the officials described the information as preliminary.

The Pentagon declined to comment, citing "operational security reasons."

Friday's attack triggered the first US air strikes to support the Syrian force. At the time, the US military said the fighters repelled the attack, without citing casualties among the US-trained force.

Defending the US-trained fighters could become a growing job for United States, which has been waging air strikes against Islamic State targets in Syria.

US officials disclosed to Reuters on Sunday that the United States has decided to allow air strikes to help defend against any attack on the US-trained Syrian rebels, even if the attackers come from forces loyal to Syrian President Bashar al-Assad.

US President Barack Obama has long sought to avoid any direct US military confrontation with Assad's forces, focussing instead on the battle against Islamic State.

The Pentagon, State Department and White House have so far declined to publicly detail the rules of engagement in Syria.

Still, the Obama administration appeared on Monday to play down the chances that Assad's forces would target the US-backed rebels and noted that his military had not fired on US-led coalition aircraft bombing Islamic State targets in Syria.

"So far, we have seen the Assad regime abide by the admonishment that we have offered to not interfere with our activities inside of Syria," said White House spokesman Josh Earnest.

The US 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 US 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, which is focussing 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 US recruits.

The suspected militants from Nusra Front attacked US-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 US officials who disclosed the death of the US-trained Syrian fighter said Division 30 also suffered casualties.