Vice President Joe Biden speaks during The American Legion's annual convention at the George R. Brown Convention Center in Houston, Aug. 27, 2013. Credit: Johnny Hanson/Houston Chronicle/AP Photo

Vice President Joe Biden today said there's "no doubt" that Bashar al-Assad's regime is responsible for the recent chemical weapons attack on Syrian civilians, as the Obama administration weighs its response.

"There is no doubt that an essential international norm has been violated - violated. Chemical weapons have been used," the vice president told the American Legion National Convention in Houston. "And there is no doubt who is responsible for this heinous use of chemical weapons in Syria: the Syrian regime."

ABC NEWS FULL COVERAGE OF THE CRISIS IN SYRIA

"For we know that the Syrian regime are the only ones who have the weapons - have used chemical weapons multiple times in the past, have the means of delivering those weapons, have been determined to wipe out exactly the places that were attacked by chemical weapons," he continued. "And instead of allowing U.N. inspectors immediate access, the government has repeatedly shelled the sites of the attack and blocked the investigation for five days."

President Obama believes that "those who use chemical weapons against defenseless men, women and children should and must be held accountable," Biden said.

The vice president has been in contact with his foreign counterparts as the Obama administration contemplates how to hold Syria accountable.