The issue focused on political violence in Syria. The United States called on Russia to stop military operations in Syria.

In an interview with CNN on Sunday, British Prime Minister David Cameron said he had never thought that President Bashar al-Assad would use chemical weapons in his civil war.

"In my view, it's no longer just war and no longer just political violence but what he's doing is criminal," Cameron said.

The United States has called for military action against Syria in recent days.