THE SYRIAN REGIME of Bashar al-Assad has suffered a series of blows in recent days: defections of generals and an ambassador; a rebel offensive that has turned parts of Damascus into a war zone; and, on Wednesday, an apparent bombing that killed at least three of Mr. Assad’s close associates, including his brother-in-law. Many observers speculated that the regime could finally be crumbling; Defense Secretary Leon Panetta said the situation was “rapidly spinning out of control.”

The regime’s quick demise is to be much wished for — but it is not something that can be counted upon. Even less probable is the managed transition the Obama administration is banking on, in which Mr. Assad and his immediate circle would depart, leaving behind an intact administration and army to negotiate a settlement with the rebels. More likely the regime will now escalate its military assaults, using weapons it has held back until now, such as its heaviest artillery and fixed-wing aircraft. As Sergei Lavrov, the foreign minister of Mr. Assad’s ally Russia, bluntly put it Wednesday, “Assad will not go on his own, and our Western partners don’t know what to do about that.”

Mr. Lavrov and his boss, Vladimir Putin, are blocking the feeble initiative that Western members of the U.N. Security Council support: a resolution that would renew the mandate of an observation force in Syria, change its mission to overseeing a political transition and provide for sanctions if the Assad regime refuses to cooperate. The Obama administration has suggested that it will allow the U.N. mission to expire Friday if Russia does not accept the sanctions provision, but in private, Western diplomats are waffling, suggesting that it would be best to keep the mission alive even if it means caving in to Moscow, as has happened repeatedly during this crisis.

There is a reasonable argument to be made for preserving a U.N. structure in Syria that could be built upon when the time is right. When, as seems increasingly likely, the regime is defeated, Syrians might want international help in setting up a new government, reconciling what are now polarized sectarian factions, and perhaps keeping the peace. But perpetuating a sterile and toothless diplomatic process merely gives Mr. Assad cover to go on waging civil war while preventing potentially more effective international action.

If the Obama administration wishes to save lives in Syria, it should support the creation of safe zones near the border where civilians can take refuge. If it wishes to speed the end of the Assad regime, it should provide the opposition with weapons that could tip the military balance. If what it mainly wants is to avoid getting involved in the conflict, despite Syria’s vital importance to U.S. interests in the Middle East, it should, at least, stop supporting diplomacy whose only beneficiaries are Vladimir Putin and Bashar al-Assad.