TEHRAN, YJC. -- US President Barack Obama issued a new warning to Syria Friday that using chemical weapons would be a "game changer" as he faced rising pressure at home and abroad to intervene in the civil war.
But a day after US officials said they suspected that the deadly agent sarin had already been fired off in small-scale attacks, Obama warned Washington must act prudently, and establish exactly if, how and when such arms were used.
Obama, who had previously told Syrian President Bashar al-Assad 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, even as other official comments and media suggested that is exactly what had happened.
Obama did reiterate that the use of chemical weapons would be "a game changer," as he met Jordan's King Abdullah II in the Oval Office.
"I think all of us, not just in the United States but around the world, recognize how we cannot stand by and permit the systematic use of weapons like chemical weapons on civilian populations," he said.
But the US leader, who has been reluctant to plunge the US military into action in Syria after extricating it from Iraq, warned: "We have to act prudently. We have to make assessments deliberately."
"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 defense official said on condition of anonymity.
The official was referring to assertions -- later proven false -- by former president George W. Bush's administration of weapons of mass destruction in Iraq, the justification for a 2003 invasion that brought eight years of war that killed nearly 4,500 US soldiers and tens of thousands of Iraqis.
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.