International tensions over chemical weapons use in Syria have worsened after UN weapons inspectors came under sniper fire as they sought to investigate a deadly attack blamed by Western nations on the regime of president Bashar Assad.
Prime Minister David Cameron is breaking off from his holiday to continue a round of calls with world leaders amid mounting speculation that the UK could join international military action.
He will chair a meeting of the National Security Council on Wednesday to discuss potential responses to the deadly attack, which killed hundreds of people, but Foreign Secretary William Hague declined to rule out air strikes within days.
Downing Street said a decision would be made on Tuesday over whether to recall Parliament amid increasingly vocal demands from MPs on all sides to be given the chance to pre-approve any UK involvement in military action.
Mr Hague said force may be the only remaining option after the failure of diplomatic efforts to end the bloody violence in Syria, insisting that it could be deployed legally even without Russian support at the UN Security Council.