WASHINGTON - Secretary of State John Kerry declared Monday that there was "undeniable" evidence of a large-scale chemical weapons attack in Syria, toughening the Obama administration's criticism of Bashar Assad's regime and outlining a justification for possible U.S. military action.
Kerry, speaking to reporters at the State Department, said last week's attack was a "moral obscenity" that "should shock the conscience" of the world. Officials said there was very little doubt that the attack was perpetrated by the Syrian government.
"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.
The international community appeared to be considering a response that would punish Assad for deploying deadly gases, not sweeping actions aimed at ousting Assad 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.
"There is not a military solution to that conflict," White House spokesman Jay Carney said.
The Obama administration was moving ahead even as a United Nations team already on the ground in Syria collected evidence from last week's attack. The U.S. said Syria's delay in giving the inspectors access rendered their investigation meaningless and officials said the administration had its own intelligence confirming chemical weapons use.
"What is before us today is real and it is compelling," Kerry said. "Our understanding of what has already happened in Syria is grounded in facts."
The U.S. assessment is based in part on the number of reported victims, the symptoms of those injured or killed and witness accounts. Administration officials said the U.S. had additional intelligence confirming chemical weapons use and planned to make it public in the coming days.
Syrian President Bashar Assad has denied launching a chemical attack. The U.N. team came under sniper fire Monday as it traveled to the site of the Aug. 21 attack.