US says 'no evidence' Syria rebels used chemical weapons

The United States said Tuesday it had seen "no evidence" that Syrian rebels have used chemical weapons and warned it would be "totally unacceptable" for the regime in Damascus to use such arms.

Responding to claims by the Syrian government and its ally Russia, White House spokesman Jay Carney said Washington has "no evidence to substantiate the charge that the opposition has used chemical weapons."

The Syrian government claimed that 25 people were killed in a chemical weapons attack by rebels in Aleppo, which the opposition denied, saying the regime might have used the banned weapons.

Carney reiterated President Barack Obama's longstanding warning that if the regime of President Bashar al-Assad used chemical weapons "there will be consequences and they will be held accountable."

"It is important that as fighting in Syria intensifies and the regime becomes more desperate, that the United States and the international community make absolutely clear to Assad that the use of chemical weapons would be totally unacceptable," he said.