The responsible role of a lone superpower is not to pick sides in a civil war; it’s to help enable conflict resolution while maintaining a policy of neutrality. Instead, the United States came down on one side of a regional sectarian conflict, inadvertently fomenting Sunni hubris and Shiite fear — the same effects (but in reverse) caused by America’s involvement in the Iraq war.

Unlike in Tunisia, Egypt and Libya, the revolution in Syria involves upending a sectarian political order, and therefore it disrupts the fragile sectarian balance within the region. Absent “boots on the ground,” supplying rebels with arms or establishing a no-fly zone are half-measures that are unlikely to advance an endgame that serves American interests or alters Mr. Assad’s calculus to step aside — all the while, intensifying the lethality of the conflict without contributing toward a decisive end.

More important, by arming the rebels, Mr. Obama is not only placing the United States in an open proxy war with Russia and Iran, but also raising the stakes and consequently jeopardizing broader and more valuable American interests.

THERE is no doubt that weakening Mr. Assad’s allies, like Iran and Hezbollah, is in the United States’ interest. But intervening in Syria could also harm much more important American goals like securing Russia’s cooperation in addressing Iran’s nuclear program and maintaining stability in Iraq. There is also the risk that intervention will become counterproductive. Empowering American-favored rebel forces to confront the influence of the hard-line Islamist groups that are also fighting against Mr. Assad may backfire and intensify rivalries, causing the fault lines of the civil war to break down even further and turn the increasingly dominant hard-line Islamists against Western-backed rebels. Mr. Assad will then be fighting an insurgency that is fighting itself.

Strangely, despite having committed to arming the rebels, Mr. Obama has yet to exhaust diplomatic efforts, which were inadequate and poorly constructed from the start. The White House’s actions and rhetoric have deprived diplomacy of its most basic prerequisites. Once it called for Mr. Assad to step down in August 2011, the United States fully abdicated the role of a credible arbiter — the core ingredient for eventually moving civil wars toward power-sharing arrangements. Then Washington insisted that Mr. Assad’s departure was required for a political transition to begin. (Its position only recently evolved; now America believes negotiations must end with Mr. Assad’s departure.)

But what’s the point of negotiating a political settlement if the outcome is already predetermined? In order for diplomacy to gain traction, it is the United States, not Russia, that must make the greater compromise and rescind its demands about Mr. Assad’s stepping down as a predetermined outcome.

His current term as president will expire in May 2014, which could provide a face-saving mechanism for a political transition to take place while keeping the institutions of the state intact. If the United States and Russia could agree on that, negotiations could then expand to involve regional Sunni and Shiite powers, who could rein in their proxies in Syria, and finally to a local level, mediating between Assad loyalists and rebels.