John McCain: Syria Using Chemical Weapons Would Be 'Most Horrendous Act' Of The Century (VIDEO)

Speaking about reports that Syria is preparing chemical weapons for potential use against its people, Sen. John McCain (R-Ariz.) warned that the world may be "on the precipice" of "the most horrendous act" of this century.

"I'm always skeptical of intelligence -- after all, back in 2007, our intelligence community said the Iranians are no longer pursuing nuclear weapons," he said Thursday night on Fox News' "On The Record with Greta Van Susteren." "But in this case, I think there is so much overwhelming ... including human intelligence ... that I don't think there is any doubt this is a -- we are on the precipice of one of the more horrendous acts, or the most horrendous act, certainly, of the 21st century."

On Wednesday, multiple news sources, citing unnamed U.S. officials, reported that Syria's military had loaded precursor chemicals for sarin, a deadly nerve gas, into aerial bombs and were awaiting orders from President Bashar Assad.

Sarin is a nerve agent, meaning it attacks the body's nervous system. The deadly substance is classified as a weapon of mass destruction by the United Nations, and its production is banned under the United Nations Chemical Weapons Convention of 1993.

Earlier on Thursday, McCain held a press conference, in which he said he was "deeply disturbed" by the news that Syria may be preparing chemical weapon stockpiles.

U.S. Defense Secretary Leon Panetta said Thursday that U.S. officials were very concerned about the possibility of chemical warfare in Syria.

"The whole world is watching very closely," Panetta said. "And the president of the United States has made it very clear, there will be consequences -- there will be consequences if the Assad regime makes the terrible mistake by using these chemical weapons on their own people."