A senior US administration official on Tuesday accused Russia of embarking on a misinformation campaign designed to "confuse the world" about what Washington says is the Syrian regime's use of sarin against its own people. 

Speaking on condition of anonymity to discuss sensitive intelligence matters, the official said that Moscow was systematically trying to deflect blame away from the regime and onto rebels and the Islamic State group -- against all evidence.

The official added that US intelligence does not believe that the Islamic State group has sarin, the powerful chemical agent Washington is "confident" was used against the rebel-held town of Khan Sheikhun.