The head of Syria's Western-backed opposition group is calling for immediate U.S. airstrikes targeting the Islamic State group in Syria.

Speaking at a press conference at the United Nations, Hadi Bahra says every day that passes without airstrikes in Syria allows the group the opportunity to grow.

President Barack Obama has said he will not hesitate to strike the extremist group in Syria, but so far has only ordered attacks in Iraq. The group holds roughly one third of each of the neighboring countries.

An offensive by the Islamic State militants against Kurdish areas near the Syrian frontier with Turkey this week sent 130,000 refugees fleeing across the border.

Bahra, who heads the Syrian National Coalition, urged more urgent action Monday to avert catastrophe.