The UK Parliament is to be recalled on Thursday to discuss possible responses to a suspected chemical weapons attack in Syria.
David Cameron cut short his holiday to deal with the Syrian crisis
David Cameron said MPs would vote on a "clear motion", amid calls for action against the Assad government.
The UK is considering military options following last week's suspected attack, which is being investigated by the UN.
The Syrian government said it was not responsible and the US and others were using it as an excuse to attack it.
The US has said there is "clear" evidence that the Assad government was behind last week's attack on the outskirts of Damascus but Russia, a key ally of Syria, has questioned this.
UN weapons inspectors are continuing to examine the scene of the alleged attacks, which the Syrian authorities have blamed on opposition fighters.
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After cutting short his holiday to deal with the crisis, the prime minister announced that the House of Commons Speaker, John Bercow, had granted his request for Parliament to be recalled from its summer recess four days early.
Mr Cameron wrote on Twitter: "Speaker agrees my request to recall Parliament on Thurs. There'll be a clear Govt motion & vote on UK response to chemical weapons attacks."
Mr Cameron has been holding meetings with senior colleagues, including his deputy Nick Clegg and Foreign Secretary William Hague, ahead of a meeting of the National Security Council on Wednesday.
Downing Street has said discussions are continuing with international allies on what to do next and that no decision has been taken on any response. However, the armed forces are drawing up contingency military plans.
It is understood the most likely military response to Wednesday's suspected chemical weapons attack would be a one-off or limited guided missile strikes on Syrian military targets fired from US Navy warships.
Thursday's Commons vote on the issue would not be legally binding but No 10 sources said the prime minister would listen to the will of Parliament amid concerns from MPs from all parties about the consequences of military intervention.
http://www.bbc.co.uk/news/uk-23851292
