chemical weapons attack in a rebel-held suburb of the Syrian capital of Damascus.
The U.S. has said a sarin gas attack killed 1,429 people, including more than 400 children, based on intelligence reports. The Britain-based Syrian Observatory for Human Rights, which collects information from a network of anti-government activists in Syria, said it has been compiling a list of the names of the dead and that its toll has reached 502.
President Barack Obama said he has decided that the United States should take military action against Syria but is seeking congressional authorization for the use of force in a vote expected after Congress returns to work Sept. 9.
Here's a look at key Syria developments around the world Wednesday amid heightened tensions over potential military action:
President Vladimir Putin warned the West against taking one-sided action in Syria but also said Russia "doesn't exclude" supporting a U.N. resolution on punitive military strikes if it is proved that Damascus used poison gas on its own people. In a wide-ranging interview with The Associated Press and Russia's state Channel 1 television, Putin said Moscow has provided some components of the S-300 air defense missile system to Syria but has frozen further shipments. He suggested Russia may sell the potent missile systems elsewhere if Western nations attack Syria without U.N. Security Council backing.
Obama's request for speedy congressional backing of a military strike in Syria advanced in the Senate, hours after the commander in chief left open the possibility he would order retaliation for a deadly chemical weapons attack even if Congress withheld its approval. The authorization measure, which cleared the Senate Foreign Relations Committee on a 10-7 vote, was altered at the last minute to support "decisive changes to the present military balance of power" in Syria's civil war. It would rule out U.S. combat operations on the ground. The resolution is expected to reach the Senate floor next week, although the timetable for a vote is uncertain.
A foreign fighter in Syria said jihadis from the Caucasus have formed an independent fighting force. In a video posted online Wednesday by the Syrian Observatory for Human Rights, a man wearing a camouflage uniform is seen standing with other fighters, who he said came to Syria from the Caucasus and Russia to wage jihad. Syrian state media said a member of the national taekwondo team was killed in a mortar attack in Damascus. State news agency SANA said 27-year-old Mohammed Ali Neimeh died when a mortar shell hit a sports hall Wednesday.
Top officials from four nations harboring more than 1.8 million Syrian refugees said they badly need outside help to care for those fleeing violence. In a joint statement issued from Geneva, the foreign ministers from Iraq, Jordan and Turkey, Lebanon's social affairs minister and U.N. High Commissioner for Refugees Antonio Guterres urgently appealed for greater international support for the refugees.
Pope Francis ramped up Vatican opposition to threatened military strikes against Syria. He urged Catholics and non-Catholics to participate in his planned day of fasting and prayer for peace on Saturday, telling more than 50,000 people gathered for his weekly general audience: "Let the cry for peace rise up across the Earth!" In recent speeches, tweets and remarks, Francis has called for a negotiated settlement in Syria and has also condemned the use of chemical weapons.
Prime Minister Jean-Marc Ayrault told parliament there is no doubt the Syrian government carried out a deadly chemical attack against civilians and that failure to react would allow Assad to launch a similar attack. He spoke during a debate to rally support for a Syria strike.