The U.S. appears to be moving toward at least arming the anti-government forces in Syria trying to topple President Bashar al-Assad, and perhaps leading Western airstrikes on Syria. President Obama, long reluctant to directly involve the U.S. in Syria's bloody civil war, is being forced to reconsider in large part because of mounting evidence that sarin nerve gas or other chemical weapons have been used in the conflict.

Two apparent Israeli airstrikes on the outskirts of Damascus since Friday are ramping up the pressure — and the geopolitical tension — but the bigger impetus to act is that the use of chemical weapons, at least in large quantities, is a "red line" that Obama laid out in August — reportedly in an off-the-cuff response to a reporter's question. "Unfortunately, the red line that the president of the United States [drew] was apparently written in disappearing ink," Sen. John McCain (R-Ariz.) said on Fox News Sunday.

But what if it isn't Assad's forces using chemical weapons? On Sunday, Carla Del Ponte, a member of a United Nations commission on Syria, said that U.N. human rights investigators have uncovered "strong, concrete suspicions but not yet incontrovertible proof of the use of sarin gas." However, she told a Swiss-Italian television station, "this was used on the part of the opposition, the rebels, not by the government authorities."

If this report is true it clearly "would vindicate the president's studied approach to the Syrian conflict and reduce the political pressure on him to act immediately," says Ty McCormick at Foreign Policy. Even as the administration has conceded recently that the evidence is starting to point toward chemical weapons use, Obama and other officials have been careful to say hard proof is needed before the U.S. jumps in.

My guess is that this latest report will give the administration enough space to put plans for arming the opposition on hold. After all, what business does the United States have arming rebels who are violating international law? Even if the testimony turns out to be unreliable... it plays into the administration's fog-of-war narrative that calls for a measured and methodical approach to a crisis that is increasingly difficult to read. [Foreign Policy]

It never made sense that Assad would use just a little bit of sarin gas, "knowing about 'red lines' and a US/Saudi/Qatari/Israeli/Turk bloodlust to invade," says Daniel McAdams at Lew Rockwell's LRC Blog.

Anyone whose brain fired on more than one cylinder should have questioned why in the hell the Syrian government would use in such a limited and militarily insignificant way the one weapon it knew would likely bring on a U.S. and NATO Libya-style intervention.... On the other hand, it made all the sense in the world for the insurgents to release some sarin here and there, make some videos of the victims, and email the links to some very willing Israeli generals and McCainian rabid warhawks in the U.S. and their absurd poodles in the UK and France. [LRC Blog]

Not everyone is convinced by Del Ponte's evidence, which is based on interviews with doctors and victims in countries neighboring Syria since Assad won't let the U.N. in to investigate.

Besides, says Dexter Filkins at The New Yorker, some experts do see the logic in Assad using just a bit of sarin gas.

Joseph Holliday, a former Army intelligence officer who has studied the conflict for the Institute for the Study of War, in Washington, suggested that the regime was attempting to use the weapons in a way that would frighten the rebels but wouldn't cross the red line. "Assad has been extremely calculating with the use of force, increasing the levels of violence gradually, so as not to set off alarm bells," he said. "First it was artillery. Then it was bombing. Then it was Scuds. A year ago, he wasn't killing a hundred people a day. He's introducing chemical weapons gradually, so we get used to them." The attacks in March and April took place in areas that were either contested or held by the regime, and they killed relatively few people, at a time when, elsewhere in the country, a hundred people were dying every day.... Indeed, some experts said that the regime was using the attacks specifically to gauge the resolve of Obama and the West. "Assad appears to be testing the tactical value of his chemical arsenal," Gary Samore, who until February was President Obama's chief adviser on weapons of mass destruction, said. "But he's testing the political limits, too." [New Yorker]

What does seem clear in all of this is that there are no great options for how to help Syria, where an estimated 70,000 people have been killed and millions more have been forced from their homes. Among the anti-Assad forces are al Qaeda-inspired Islamist militants who are no fans of the U.S., and the U.S. public has no appetite for getting embroiled in another murky Mideast war.

Even McCain — who told Foxs News Sunday that "we need to have a game-changing action," and is one of the biggest proponents of intervening in Syria — seeks a somewhat limited U.S. role in the civil war: "And that is no American boots on the ground, establish a safe zone, and to protect it and to supply weapons to the right people in Syria who are fighting for obviously, the things we believe in."