A wounded Syrian man held his injured son after an air raid Thursday on the northwestern town of Saraqeb, in the province of Idlib.


WASHINGTON - Proceeding cautiously, President Obama insisted on Friday that any use of chemical weapons by Syria would change his "calculus" about U.S. military involvement in the 2-year-old civil war - but said too little was known about a pair of likely sarin attacks to order aggressive action now.

The president's public response to the latest intelligence reflected the lack of agreement in Washington over whether to use America's military to intervene in the civil war, and if so, how. But lawmakers in both parties expressed concern that inaction could embolden Syrian President Bashar Assad and perhaps other countries including North Korea and Iran.

U.S. officials declared on Thursday that the Syrian government probably had used chemical weapons twice in March in the civil war that has killed more than 70,000 people. The U.S. assessment followed similar conclusions from key allies Britain, France, Israel and Qatar.

Obama, in his first comments about the new intelligence disclosure, said Friday, "For the Syrian government to utilize chemical weapons on its people crosses a line that will change my calculus and how the United States approaches these issues."

He has issued similar warnings for months, saying the use of chemical weapons or transfer of the stockpiles to terrorists would cross a "red line" and carry "enormous consequences."

Obama added Friday that "I've meant what I said."

The president is facing pressure from a contingent of senators, led by Arizona Republican John McCain, favoring a quick, strong U.S. response. But even those lawmakers appear opposed to an American military invasion and are instead supporting creation of a protective "no-fly zone" or a narrow, safe zone inside Syria along its border with Turkey.

White House officials insisted Obama's caution was not an indication that the "red line" was shifting.

Obama met at the White House with Jordan's King Abdullah II, whose nation is suffering amid an influx of refugees spilling over its border with Syria.

The president promised to vigorously pursue more information about chemical weapons attacks, including exactly who might be responsible.

But the president set no deadline for answers.

"The president wants the facts," spokesman Jay Carney said. "And I'm not going to set a timeline because the facts need to be what drives this investigation, not a deadline."

Syrian officials denied Friday that their government forces had used chemical weapons against rebels.