Timeline: Turning points in the U.S. debate on Syria

WASHINGTON | (Reuters) - President Barack Obama backed off from an imminent military strike against Syria on Saturday to seek the approval of the U.S. Congress, in a decision that likely delays U.S. action for at least 10 days.

Following are turning points in the Obama administration's debate on whether and how to intervene in Syria's two-year civil war.
April 29, 2011 - United States slaps sanctions on Syria's intelligence agency and two relatives of President Bashar al-Assad, in Washington's first concrete steps in response to a crackdown on anti-government protests inspired by the "Arab Spring."

August 18, 2011 - For the first time, Obama calls for Assad to step down, saying: "For the sake of the Syrian people, the time has come for President Assad to step aside." Britain, France and Germany also call for Assad to go.
July 19, 2012 - U.S. Ambassador to the United Nations Susan Rice calls the Russian and Chinese vetoes of a U.N. Security Council resolution on Syria "dangerous and deplorable."
July 23, 2012 - Syria says it could use chemical weapons in response to any "external aggression" but they will not be used in Assad's campaign to crush the uprising in what appeared to be the first time that Syria acknowledges it might possess non-conventional weapons.
July 23, 2012 - Obama says Assad will be held accountable if he makes the "tragic mistake" of using Syria's stockpile of chemical weapons.
August 20, 2012 - Obama warns Assad that the use or deployment of chemical or biological weapons in his country's conflict would be a "red line" for the United States. "A red line for us is (if) we see a whole bunch of chemical weapons moving around, or being utilized. That would change my calculus," he tells reporters.
December 3, 2012 - Obama warns Assad "the world is watching" and there would be consequences if he uses chemical weapons against Syrian opposition forces. "The use of chemical weapons is and would be totally unacceptable and if you make the tragic mistake of using these weapons, there will be consequences and you will be held accountable," he says in a speech to a gathering of biological, chemical and nuclear weapons proliferation experts.
March 19, 2013 - Syria's government and rebels accuse each other of launching a deadly chemical attack near the northern city of Aleppo in what would be the first use of such weapons in the two-year conflict.
April 26, 2013 - Obama warns Assad that any use of chemical weapons in Syria's civil war would be a "game changer" but remains cautious about endorsing intelligence assessments that such weapons had been deployed.
June 8, 2013 - Syrian government troops backed by guerrillas from Lebanon's Hezbollah seize the western village of Buwayda to end rebel resistance around the strategically important town of Qusair in a success for Assad forces. The involvement of Iran-sponsored Hezbollah and gains by Syrian forces prompt renewed U.S. debate on arming Assad's opponents.
June 13, 2013 - After two months of caution about reports Syria used chemical weapons, the White House says U.S. intelligence agencies have concluded that Assad's forces indeed used such weapons, including the nerve agent sarin, on a small scale against the opposition multiple times, killing 100 to 150 people. The White House vows to increase military aid to the Syrian rebels.
August 21, 2013 - Syria's opposition accuses government forces of gassing hundreds of people by firing rockets that released deadly fumes over rebel-held neighborhoods near Damascus, killing men, women and children as they slept. If confirmed, it would be the worst chemical weapons attack in 25 years.
August 26, 2013 - Secretary of State John Kerry says all nations must stand up for accountability on the "undeniable" use of chemical weapons in Syria, where he said the government maintained custody of such weapons. "Let me be clear: The indiscriminate slaughter of civilians, the killing of women and children and innocent bystanders by chemical weapons is a moral obscenity."
August 30, 2013 - In separate statements, Obama and Kerry harshly condemn the Syrian government, saying the Aug 21. attack cannot go unpunished. Obama says: "We cannot accept a world where women and children and innocent civilians are gassed on a terrible scale," while Kerry calls Assad "a thug and a murderer." But they say any military response by the United States would be measured to avoid open-ended commitments.
August 30, 2013 - U.S. intelligence agencies publicly disclose some of the information that led to a "high-confidence" assessment that the government of Assad carried out a chemical weapons attack on neighborhoods outside Damascus, causing the deaths of an estimated 1,429 Syrians on August 21.
August 31, 2013 - Obama says he had authorized the use of military force to punish Syria, with military assets to carry out a strike in place and ready to move on his order, but he would first seek authorization from Congress. "Today I'm asking Congress to send a message to the world that we are ready to move as one nation," he said.
(Reporting by Paul Eckert; Editing by Vicki Allen)