WASHINGTON (CBSDC/AP) — Secretary of State John Kerry said Monday that it is “undeniable” that the Syrian government used chemical weapons against its own people.

Kerry’s comments come in response to a chemical attack that some Syrian activists say killed up to 1,300 people outside Damascus last week.

“What we saw in Syria last week should shock the conscience of the world,” Kerry stated.

Kerry railed against those that believed the Aug. 21 chemical attack was a fabricated event.

“Anyone who could claim that an attack of this staggering scale could be contrived or fabricated needs to check their conscience or their own moral compass,” Kerry said.

With Syrian government officials firing at United Nations investigators and not allowing them at the attack site, Kerry said that “it is too late” for President Bashar Assad’s regime to be credible and that they will be held accountable.

“Make no mistake, President Obama said there must be accountability for those who would use the world’s most heinous weapons against the world’s most vulnerable people,” Kerry said.

Kerry, who accused Assad of destroying evidence, said that Syria is capable of even more chemical attacks.

“We know that the Syrian regime maintains custody of these chemical weapons, we know that the Syrian regime has the capacity to do this with rockets,” he said.

“What is before us today is real and it is compelling,” Kerry said. “Our understanding of what is already happened in Syria is grounded in facts, informed by conscience and guided by common sense.”

Kerry revealed that the Obama administration has been in close contact with Congress and that the president has reached out to allied worldwide about the situation.

Syrian Deputy Foreign Minister Faisal Mikdad told The Associated Press that a strike against Syria would trigger worldwide “chaos.”

Earlier Monday the ranking Senate Foreign Relations Committee Republican urged a “surgical” U .S. air strike against Syria in reprisal for Bashar Assad’s alleged use of chemical weapons.

Sen. Bob Corker of Tennessee told NBC’s “Today” show that “I do think action is going to occur” militarily in response to the purported chemical weapons use last week in a Damascus suburb.

Corker said the Obama administration “feels like there’s no question chemicals were used” and says it is seeking to rally its NATO allies to support a military response.

He added, quote, “I think it should be surgical, it should be proportional. It should be responsive to what happened on the ground.”

But Corker also said, “I think we can get that right without us getting mired in a conflict.”

According to a Reuters/Ipsos poll, only 9 percent of Americans believe the U.S. should intervene in Syria militarily.

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