Syria: US troops should not be sent, says John McCain
The United States has accused the Syrian government of using chemical weapons, including the nerve agent sarin, against its opponents.
A White House statement said the latest intelligence suggested up to 150 people had been killed in a small number of chemical attacks.
US Deputy National Security Advisor Ben Rhodes official said a red line had been crossed, and President Obama had decided to provide more military support to the rebels.
Senators John McCain and his fellow Republican Lindsey Graham have urged President Obama to respond by sharply increasing support for the Syrian opposition but stop short of sending US troops.