PRESIDENT OBAMA approached his address to the country Tuesday night in a deep political hole — one largely of his own digging. As the president and his aides have argued for a military response to Syria’s use of chemical weapons, support for a strike among Americans and members of Congress has decreased. That’s largely because Mr. Obama and his administration offered stumbling, improvised and often inconsistentexplanations for why military action is needed and what effect it would have. And that was before Monday’s dizzying pivot toward an ad hoc diplomatic initiative to place Syria’s arsenal under international supervision.

Mr. Obama’s short speech, scheduled before the diplomatic option appeared, restated some of the arguments for using force while simultaneously announcing that his administration would pursue a U.N. Security Council resolution formalizing a plan for Syria to give up its chemical weapons. His formulations remained inconsistent: While declaring that “our ideals and principles, as well as our national security, are at stake in Syria, along with our leadership of a world where we seek to ensure that the worst weapons will never be used,” Mr. Obama reiterated that any military strike would be limited and would not aim at toppling the Syrian regime. The president said he had ordered U.S. forces to remain ready to act in the event diplomacy fails. But he did not explicitly reject a demand by Russian President Vladimir Putin that the United States forswear military action in exchange for Syria’s agreement to give up its weapons, and he asked Congress to postpone an authorizing vote.

In sum, the president’s approach to Syria remains muddled. When Russia seized on an offhand remark by Secretary of State John F. Kerryto launch the diplomatic plan Monday, the administration expressed deep skepticism that it was feasible. Now, having declared Bashar al-Assad’s regime as criminal and the government of Vladi­mir Putin as obstructive, the White House appears prepared to make them its primary interlocutors in a long-shot bid to sequester the chemical agents — something that Mr. Kerry on Monday said “can’t be done.” Mr. Obama argued that the threat of force had produced the Russian diplomatic proposal. But he didn’t set firm parameters or a time limit for completing a deal.

Despite the contradictions, we believe Mr. Obama had little choice but to put the disarmament initiative to the test. Unlikely as success may be, the potential benefit of controlling and eventually eliminating a large and dangerous arsenal can’t be dismissed. And a Syrian refusal to comply would provide more solid ground for using force.

At the same time, Mr. Obama must integrate the disarmament initiative into a broader strategy for Syria and the region around it. The president promised “to redouble our efforts to achieve a political solution” to the Syrian civil war, but he offered no plausible path toward that goal. The administration proposes negotiations between the regime and rebels, with the participation of Russia and possibly Iran. But the Assad regime will not yield power — a necessary part of any conceivable deal — unless the military balance is tipped against it. Can a transition strategy for Syria be advanced during what inevitably would be a complex and lengthy process of negotiating the regime’s declaration and rendition of chemical weapons to international inspectors? If so, Mr. Obama did not explain how.