Below is an account of the main developments surrounding accusations of the use of chemical weapons in Syria, which has been wracked by armed conflict for the past two years:
- July 23: The Syrian regime acknowledges for the first time that it has chemical weapons and threatens to use them in case of a Western military intervention, but never against its own people.
- August 20: US President Barack Obama warns Syria of "enormous consequences" if it resorts to chemical weapons, and says the United States would regard any recourse by Damascus to its deadly arsenal as crossing a "red line" which would result in US action.
- December 3: NATO and the United States warn Syria against using its chemical weapons, as a US official says that Syria has begun mixing chemicals that could be used to make sarin, a deadly nerve agent.
- December 24: Russian Foreign Minister Sergei Lavrov says it would be "political suicide" for the government of Syrian President Bashar al-Assad if it used chemical weapons against the armed opposition, but that "I do not believe Syria would use chemical weapons".
- January 30: the Israeli air force bombards a site of ground to air missiles and an adjacent military complex near Damascus suspected of holding chemical agents, with Israel saying it feared the transfer of weapons to the Lebanese Shiite movement Hezbollah, according to a US official.
- March 19: The government and rebel forces accuse each other of using chemical weapons for the first time, but the United States says it has seen "no evidence" of such action.
- March 20: Obama warns the Damascus regime it would be held accountable for any use of chemical weapons against civilians in Syria, which would be a "grave and tragic mistake" and a "game-changer."
- March 21: the United Nations says it will open an investigation into an alleged chemical weapons attack in Syria.
- April 8: UN Secretary General Ban Ki-moon says the UN inspection team is in Cyprus and ready to deploy. Syria rejects the mission as proposed by Ban.
- April 25: The White House says that Syria has likely used chemical weapons against rebel forces on a "small scale," during the conflict, while emphasizing US spy agencies are still not 100 percent sure.
UN leader Ban renews an "urgent call" for Syria to let inspectors into the country.
- April 26: British Prime Minister David Cameron says that growing evidence of the use of chemical weapons by the regime is "extremely serious". Israel urges the US to "take control of Syria's chemical weapons arsenal".
Syria's opposition urges the UN Security Council to take immediate action.
Obama is awaiting a "definitive judgement" on whether the Syrian regime used chemical weapons against rebels before taking action, the White House says.