In this image taken from video, Britain's Prime Minister David Cameron, center, speaks during a debate on Syria, in Britain's parliament, London, Thursday, Aug. 29, 2013. (AP Photo / PA)
British Prime Minister David Cameron leaves 10 Downing Street in London to be driven to Parliament for a debate and vote on Syria on Aug. 29, 2013. (Associated Press)
Russian President Vladimir Putin, left, looks toward British Prime Minister David Cameron, center, and U.S. President Barack Obama during group photo with G-8 leaders on Tuesday, June 18, 2013, in Enniskillen, Northern Ireland. (AP Photo/Evan Vucci)
British Prime Minister David Cameron, left, shakes hands with Russian President Vladimir Putin during a press conference at 10 Downing Street in London, Sunday, June 16, 2013. Cameron had talks with Russian President Putin on the Syrian crisis amid fears that differences between Moscow and the West are pushing the two sides toward a new Cold War. (AP Photo/Anthony Devlin)
Britain's Prime Minister David Cameron speaking to the media outside 10 Downing St. in London, Thursday, May 23, 2013. (AP Photo/Alastair Grant) ** FILE **