Mr Zarif said conflict between Sunnis and Shias was “the most serious security threat not only to the region but to the world at large”. “I think we need to come to understand that a sectarian divide in the Islamic world is a threat to all of us.” Sectarian tension between Shia and Sunni Muslims has been a fact of life for more than 1,000 years, says the BBC’s Middle East Editor Jeremy Bowen. But upheaval in the Middle East this century, especially since the US-led invasion of Iraq in 2003, has made it much worse. http://www.bbc.co.uk/news/world-middle-east-24893808