President Obama today warned Syrian President Bashar al-Assad that the use of chemical weapons by his regime would be "totally unacceptable" and that he would be "held accountable."

"I want to make it absolutely clear to Assad and those under his command, the world is watching," Obama said at the Nunn-Lugar Cooperative Threat Reduction symposium in Washington.

"The use of chemical weapons is and would be totally unacceptable. And if you make the tragic mistake of using these weapons, there will be consequences, and you will be held accountable," he said.

The president stopped short of detailing those consequences.

The warning comes as U.S. intelligence has detected Syrian movement of its chemical weapons stockpile in recent days.

Earlier today the White House reiterated that use or proliferation of chemical weapons by the Syrian military is a "red line" that would prompt U.S. action.

"We will continue to support the legitimate aspirations of the Syrian people, engaging with the opposition… providing them with humanitarian aid and working for a transition to a Syria that's free of the Assad regime," Obama said.