The United States has decided to allow airstrikes to defend Syrian terrorists trained by the US military from any attackers, even if the enemies hail from the Syrian regular army, US officials said on Sunday.

The United States has decided to allow airstrikes to defend Syrian terrorists trained by the US military from any attackers, even if the enemies hail from the Syrian regular army, US officials said on Sunday.

The decision by President Barack Obama, which could deepen the US role in Syria's conflict, aims to shield a still-fledging group of Syrian fighters armed and trained by the United States to battle ISIL militants -- not forces loyal to Assad.

The first batch of US-trained forces deployed to northern Syria came under fire on Friday from other militants, triggering the first known US airstrikes to support them.

US officials, speaking on condition of anonymity to confirm details of the decision, first reported by the Wall Street Journal, said the United States would provide offensive strikes to support advances against ISIL targets.

The United States would also provide defensive support to repel any attackers.