President Barack Obama's administration insists that Syrian President Bashar Assad's government carried out a chemical weapons attack against his own people. Obama has said that the United States was prepared to take military action, but he has stressed that diplomatic measures should be taken first. Assad's government denies the allegations and insists the rebels are to blame for any chemical attack. Russia is among the countries that have supported the Assad regime.
A look at the latest developments and how it got to this point:
The Syrian conflict
Now in its third year, the civil war in a small country with a population of about 23 million is complicated and brutal. There are heavy civilian casualties on both sides.
The conflict has increasingly taken on sectarian tones as rebels, some of them Islamic extremists, fight government loyalists. It's essentially a regional proxy war increasingly fought along sectarian lines, pitting Sunni against Shiite Muslims, and threatening the stability of Syria's neighbors.
By mid-2011, a loose coalition of rebels and anti-government tribal groups had formed the Free Syrian Army, whose goal was to topple Assad. As the violence increased, more people fled the country.
Rebels appeared to be gaining the upper hand, and they occupied more and more territory. But in the past few months, the military scored a string of victories, and their offensives pushed many rebels back into the Damascus suburbs. Assad's government increased its pressure on rebels as pro-democracy Arab Spring movements swept through the region last year.
The United Nations estimates that nearly 2 million people have fled, many into Lebanon.
Anti-Syrian regime protesters chant slogans during a Feb. 24, 2012, demonstration against Syrian President Bashar Assad and to show their solidarity with the Syrian people in the northern city of Tripoli, Lebanon. THE ASSOCIATED PRESS
Obama's 'red line'
Last year, Obama said that Assad's use of chemical weapons would cross a red line, suggesting greater U.S. intervention. This June, the White House said it had conclusive evidence that Assad used chemical weapons against rebel fighters, and Obama decided to respond by authorizing the arming of Syria's rebels.
The move promised to deepen U.S. involvement in the conflict and heightening U.S. tensions with Russia, a staunch ally of Assad. It was a turning point for the U.S., which up to that point had avoided getting drawn into the conflict militarily. A chief U.S. concern had been that U.S.-supplied weapons could fall into the hands of al-Qaida-linked militants fighting alongside the rebels.
Black columns of smoke rise from heavy shelling in the Jobar neighborhood in East of Damascus, Syria, on Aug. 25. THE ASSOCIATED PRESS
On Aug. 21, the Obama administration says, Assad's government unleashed a chemical attack outside Damascus. The government of Syria denies there were any chemical attacks.
Estimates of the dead have varied. Activists and those who live in the area have said well over 1,000 people died in the attacks. Secretary of State John Kerry put the death count at 1,429, of which he said 426 were children. The nonpartisan humanitarian group Doctors Without Borders has put the death toll at 355 people. The Syrian Observatory for Human Rights, one of the main groups monitoring casualties in Syria, has said it was able to confirm 502 deaths, identifying victims by name.
President Barack Obama addresses the nation in a live televised speech from the East Room of the White House on Sept. 10. President Obama blended the threat of military action with the hope of a diplomatic solution as he works to strip Syria of its chemical weapons. THE ASSOCIATED PRESS
Military vs. diplomacy
Obama announced in late August that he would seek congressional approval for military strikes targeted at the Assad regime, even though he had the authority to act alone. His decision sparked protests around the world — including in Columbia — both for and against a U.S.-led attack. Members of Congress had sharply divergent opinions about whether to give Obama the go-ahead, with the mid-Missouri delegation expressing skepticism.
On Sept. 10, however, Obama asked Congress to delay the vote, instead touting diplomatic steps. But he also insisted the U.S. military would keep the pressure on Assad "and be ready to respond."
Marathon negotiations, meanwhile, between U.S. and Russian diplomats in Geneva produced a sweeping agreement that would require one of the most ambitious arms-control efforts in history. While the deal strengthened Obama's inclination to find answers through diplomacy rather than military means, it took time and tough negotiations for the deeply divided U.N. Security Council to work out the details of the resolution.
After 2 1/2 years of inaction and paralysis, the agreement, reached Thursday, represents a breakthrough for the council and rare unity between Russia and the United States. The world's chemical weapons watchdog approved the plan Friday, and the Security Council passed what U.N. Secretary-General Ban Ki-moon called "the first hopeful news on Syria in a long time."