President Obama has authorised air surveillance flights over Syria in the battle against Islamic State (IS) fighters, according to US media reports.

Reconnaissance missions have already begun, some sources say, although officially the White House is still considering its strategy – with military air strikes in Syria against IS extremists an apparent option.

“To your question, can they be defeated without addressing that part of their organisation which resides in Syria? The answer is no,” Obama’s top military advisor, General Martin Dempsey, told a news conference.

“And that will come when we have a coalition in the region that takes on the task of defeating ISIS over time. ISIS will only truly be defeated when it is rejected by the 20 million disenfranchised Sunnis that happen to reside between Damascus and Baghdad,” added Dempsey, Chairman of the US Joint Chiefs of Staff.

An American air campaign against IS in Iraq is already underway.

But the beheading of US journalist James Foley and the Syrian regime’s willingness to cooperate – despite its pariah status for the West – could mean cross-border air strikes by the US sooner rather than later.