|Saudi Arabia often torture citizens under its harsh laws|
Mr Jubeir told the BBC that there was "no doubt" Mr Assad had to go. "He will go either through a political process or he will be removed by force," he said.
Earlier American Secretary of State John Kerry said the US was intensifying diplomatic efforts to end the "hell" of Syria's civil war even as it increases support for moderate rebels.
Foreign ministers from the UK, France, Germany, Egypt, Lebanon and the EU have also confirmed they will attend the meeting, and other Middle Eastern powers are also expected.