Use of chemical weapons red line for US: Obama to Syria

United States President Barack Obama has issued the toughest warning to his Syrian counterpart Bashar al-Assad, saying the use of chemical or biological weapons by Damascus would be a 'red line' that would change his calculus significantly and provoke a foreign military intervention.

"We cannot have a situation where chemical or biological weapons are falling into the hands of the wrong people," Obama told reporters at the White House on Monday.

"We have been very clear to the Assad regime -- but also to other players on the ground -- that a red line for us is we start seeing a whole bunch of chemical weapons moving around or being utilised," Obama said, outlining for the first time the point at which his administration could feel forced to intervene militarily in the Arab country's raging conflict.

Obama, who has not ordered any armed US intervention yet, said: "We have communicated in no uncertain terms with every player in the region, that that's a red line   for us, and that there would be enormous consequences if we start seeing movement on the chemical weapons front, or the use of chemical weapons. That would change my calculations significantly."

"That would change my calculus; that would change my equation," Obama said.

He said that US officials are monitoring the situation 'very carefully' and have put together a number of contingency plans. Reiterating that the Assad regime in Syria "has lost legitimacy" and "needs to step down", Obama alleged that authoritarian Syrian regime has doubled down in violence on his own people.

Since the Syrian crisis began 17 months ago, more than 20,000 people have been killed, opposition activists claim.