It makes sense for President Obama to order a delay of any military action against Syria and explore a diplomatic alternative. However, his request that Congress delay a vote on backing such military action appears more a product of political pragmatism than foreign policy acumen.

Three priorities are in play: Preventing Syrian President Bashar Assad from using chemical weapons against his people again; keeping those weapons out of the hands of jihadist terrorists; and weakening Mr. Assad, leading to his eventual ouster, ideally with moderate forces taking control.

Russia and the United States share at least one of those priorities: keeping terrorists from obtaining poison gas. That may account for the recent diplomatic opening. Russia is ostensibly working with its ally, Syria, on a plan under which the Assad regime would relinquish control of its chemical arsenal.

A Syrian commitment to do so, backed with a United Nations resolution, would be a significant development. Securing those chemicals scattered across a large country, in the midst of a civil war, would be problematic. Yet even short of that, Mr. Assad would still be boxed in. With a U.N. resolution in place, any use by his military of chemical weapons would be a blatant violation. Under that scenario, the United States should be able to generate broad international support for a response.

The question is how serious are Mr. Assad and Russian President Vladimir Putin? Is this a stalling tactic to delay a U.S. military strike or a genuine diplomatic opening? If Russian/Syrian demands prove unreasonable, if a delay strategy becomes obvious, President Obama must be prepared to return to his original policy of a military response to degrade the Syrian military's ability to launch future chemical attacks.

Ideally, President Obama would have in his back pocket the backing of Congress for a military action if diplomacy fails. That unified threat of force could motivate a deal. That the president is instead delaying congressional action is recognition he likely would not win the vote.

But both Russia and the United States have plenty of incentive to reach a genuine agreement and secure the chemical arsenal. A worst-case scenario is that Mr. Assad is toppled and radical Islamic enemies of Russia and the United States take control of the chemical weapons.