WASHINGTON — Secretary of State John Kerry on Monday outlined the clearest justification yet for U.S. military action in Syria, saying there was "undeniable" evidence of a large-scale chemical weapons attack, with intelligence strongly signaling that Bashar Assad's regime was responsible.
Kerry, speaking to reporters at the State Department, said last week's attack "should shock the conscience" of the world.
"The indiscriminate slaughter of civilians, the killing of women and children and innocent bystanders by chemical weapons is a moral obscenity. By any standard, it is inexcusable and — despite the excuses and equivocations that some have manufactured — it is undeniable," said Kerry, the highest-ranking U.S. official to confirm the attack in the Damascus suburbs that activists say killed hundreds of people.
"This international norm cannot be violated without consequences," he added.
Officials said President Barack Obama has not decided how to respond to the use of deadly gases, a move the White House said last year would cross a "red line." But the U.S., along with allies in Europe, appeared to be laying the groundwork for the most aggressive response since Syria's civil war began more than two years ago.
Two administration officials said the U.S. was expected to make public a more formal determination of chemical weapons use on Tuesday, with an announcement of Obama's response likely to follow quickly. The officials insisted on anonymity because they were not authorized to publicly discuss the internal deliberations.
The international community appeared to be considering action that would punish Assad for deploying deadly gases, not sweeping measures aimed at ousting the Syrian leader or strengthening rebel forces. The focus of the internal debate underscores the scant international appetite for a large-scale deployment of forces in Syria and the limited number of other options that could significantly change the trajectory of the conflict.