US Senator McCain: 'Syria red line has been crossed'

US Senator John McCain has said Syria's apparent use of chemical weapons, meant "a red line" had been crossed.

US Defence Secretary Chuck Hagel said American intelligence believed "to some degree of varying confidence" that Syria had used chemical weapons.

President Barack Obama warned in December that Syrian President Bashar al-Assad would face "consequences" if he used such weapons.

"It's pretty obvious that red line has been crossed," said Senator McCain.

The senator went on to recommend arming the opposition, a step the White House has been reluctant to take.

He also urged taking steps to ensure that Syria's chemical weapons did not fall into the wrong hands.