Homs lies along a key highway that connects Damascus with the coastal city of Latakia, a regime stronghold.
Some US lawmakers want the US to establish a no-fly zone over Syria. Gen. Martin Dempsey, chairman of the Joint Chiefs, questioned Tuesday whether that would do much to reduce Syrian attacks on civilians, never mind that it won't be easy.
Bashar Assad almost certainly crossed a 'red line' by using sarin or some other chemical weapon against his own people, President Obama said in April. The casualty toll from the latest suspected use suggests sarin henceforth will be associated with Syria and Mr. Assad.
The Israeli military says its evidence shows that the Syrian regime used sarin gas during a March clash with rebels, reversing earlier reports that no such weapons had been used.