THE US is worried that a desperate Syrian President Bashar al Assad may resort to the use of chemical weapons, or lose control of them, Secretary of State Hillary Clinton has said.

After a meeting of Nato foreign ministers at which the Western military alliance agreed to send Patriot anti-missile batteries to Syria's neighbour, Turkey, Ms Clinton said Washington had made clear to Syria use of chemical weapons is a "red line" for the US.

"Our concerns are that an increasingly desperate Assad regime might turn to chemical weapons, or might lose control of them to one of the many groups that are now operating within Syria," Ms Clinton said.

Loading article content

"And so as part of the absolute unity that we all have on this issue we have sent an unmistakable message that this would cross a red line and those responsible would be held to account."

Saying a political transition in Syria needed to start as soon as possible, Ms Clinton said the US would do what it could to support the new opposition coalition, the Friends of Syria.