WASHINGTON – The United States on Monday said it has used air power in Syria in defence of allied rebel groups, signalling deeper involvement in the country's brutal four-year civil war.
The Pentagon confirmed that an air strike was carried out on Friday in support of the New Syria Force, a US-allied group.
"We'll take action to defend the New Syria Force that we've trained and equipped," said Pentagon spokesman Commander Bill Urban.
He said "last Friday was the first one", referring to the air strike.
Earlier, a senior administration official said the United States had hit al Qaeda's Syrian affiliate the Al-Nusra Front in response to attack on US trained rebels.
President Barack Obama's administration said on Monday it was prepared to take "additional steps" to defend US-trained and equipped forces, warning Bashar al-Assad's government "not to interfere".
"The president approved this recently upon the recommendation of his senior military advisers," said a senior administration official.
White House spokesman Josh Earnest said Assad's government had not so far hampered US-backed forces, but he nonetheless raised the possibility of strikes against it should the need arise.
The United States, Earnest said, was "committed to using military force where necessary to protect the coalition-trained and equipped Syrian opposition fighters".
Officials argue that authority includes the ability to provide "defensive fire support".
The US has trained and equipped a number of fighters – screened and determined to be "moderate" – to operate against the jihadist Islamic State organisation.
But US-backed forces have yet to play a major role in turning the war and its fledgling local ground force has already suffered a series of reversals.
A 54-strong unit inserted into the rebels' Division 30 has come under withering attack from the Al-Nusra Front, with several members reportedly killed or captured.
Micah Zenko of the Council on Foreign Relations said the "truly significant decision" could potentially extend well beyond that small force.
Monday's announcement comes as diplomatic efforts to halt the carnage in Syria resume.
An estimated 140,000 people have died in the conflict, which began as an uprising against the Assad government but has morphed into a multipronged religious and ethnic civil war.
A UN envoy recently presented his plan to resuscitate failed talks and foreign ministers from the United States, Russia and Saudi Arabia held talks in Qatar on Monday.
The trio agreed to the "need for a meaningful political transition" according to State Department spokesman Mark Toner.
But Russian Foreign Minister Sergei Lavrov later condemned Washington's move toward a more robust involvement in Syria.
"We believe it's counterproductive to announce publicly that some US-trained armed groups... will be under the protection of the coalition's air forces," Lavrov said. -- AFP