U.S. Secretary of State John Kerry arriving in Qatar on Saturday to attend a summit of the so-called 'Friends of Syria'.<br/> <br />The summit, which brings together foreign ministers of 11 pro-rebel countries, comes in the wake of an American decision to arm some elements of the opposition.<br/> <br />The move has brought a chill to relations between Washington and Moscow.<br/> <br />Russian President Vladimir Putin warned against arming the opposition which he said included "terrorist" groups, but defended his own country's arms sale to the Syria regime.<br/> <br />The rebels say they urgently need advanced weaponry, including anti-tank and anti-aircraft weapons, to stem the recent advances made by forces loyal to President Assad.<br/> <br />But there are concerns in Western nations that such advanced weaponry could fall into the hands of jihadi groups hostile to the West.<br/> <br />A UN human rights investigator also warned on Friday, that an increased flow of arms to both sides would likely result in further w
