Failure to act in Syria risks stoking a "total war" in the Middle East, French President Francois Hollande said in a landmark speech to the European Parliament alongside German Chancellor Angela Merkel.

"What happens in Syria concerns Europe, what happens there will determine the balance of the whole region for a long time," Hollande said.

"If we leave these religious clashes between Sunnis and Shiites, they will grow. Don't think we will be sheltered, this will be a total war."