"We know that for three days before the attack, the Syrian regime's chemical weapons personnel were on the ground in the area, making preparations," Kerry said. "And we know that the Syrian regime elements were told to prepare for the attack by putting on gas masks and taking precautions associated with chemical weapons."

In addition, "we know where the rockets were launched from, and at what time," he said. "We know where they landed, and when. We know rockets came only from regime-controlled areas and went only to opposition-controlled or contested neighborhoods."

Quoting from the U.S. assessment, Kerry said the attack killed 1,429 people, including more than 400 children.

"We assess with high confidence that the Syrian government carried out the chemical weapons attack against opposition elements in the Damascus suburbs," he said.

Al-Assad's government has claimed that jihadists fighting on the opposition's side carried out the chemical weapons attacks on August 21 to turn global sentiments against it. Senior administration officials told reporters Friday there is no evidence to support that claim.

http://www.cnn.com/2013/08/30/world/europe/syria-civil-war/index.html?hpt=hp_t1