U.S. officials say more than 1,400 died in the episode, including at least 400 children, and other victims suffered uncontrollable twitching, foaming at the mouth and other symptoms typical of exposure to chemical weapons banned by international treaty. Other casualty estimates are lower, and Assad has said the attack was launched by rebels who have been fighting to drive him from power in a civil war that has so far claimed the lives of more than 100,000 civilians.
Assad's patron, Russia, has blocked U.S. attempts to rally the Security Council behind a military strike. But Monday, after a remark by Kerry, it spoke favorably about requiring Syria to surrender control of its chemical weapons, and the Syrian foreign minister did likewise.
The foreign minister, Walid al-Moallem, said Tuesday that his government was ready to turn over its chemical weapons stockpile in line with Russia's proposal in order "to thwart U.S. aggression." He also said Syria is prepared to implement a Russian proposal to put its chemical weapons arsenal under international control.
Syria has never provided an accounting of the size of its stockpile, rarely referring in public to its existence. According to an unclassified estimate by the French government, it includes more than 1,000 tons of "chemical agents and precursor chemicals," including sulfur mustard, VX and sarin gas
Obama has said frequently he has the authority as commander in chief to order a military strike against Assad regardless of any vote in Congress, and he has consistently declined to say whether he would do so if lawmakers refuse to approve the legislation he is seeking.
The response in Congress to support such a strike has been lukewarm at best — as underscored during the day when liberal Sen. Ed Markey, D-Mass., and conservative Rep. Mark Mulvaney, R-S.C., both announced their opposition.