Obama, who had previously told Syrian President Bashar al-Assad that the use of chemical weapons would cross a “red line,” promised a “vigorous” US and international probe into the latest reports.
But he appeared wary of launching military action based on initial intelligence reports of chemical weapons use.
Obama did reiterate that the use of chemical weapons would be “a game changer,” as he met Jordan’s King Abdullah II in the White House’s Oval Office.
“I think all of us, not just in the US but around the world, recognise how we cannot stand by and permit the systematic use of weapons like chemical weapons on civilian populations,” he said.
“We have to act prudently. We have to make assessments deliberately,” he cautioned.
The spectre of the invasion of Iraq, which led to an eight-year war that killed tens of thousands of Iraqis and nearly 4,500 US soldiers, looms large. The 2003 invasion was justified on the basis of claims that Saddam Hussein’s regime had weapons of mass destruction, which turned out to be false.
“We have seen very bad movies before when intelligence is perceived to have driven policy decisions that in the full light of day have proven wrong,” a US defence official said on condition of anonymity.
Adding to the political heat on Obama, the Syrian opposition urged the UN Security Council to take immediate steps, possibly even by imposing a no-fly zone.