Stephen J. Hadley, a principal at RiceHadleyGates LLC, was national security adviser in the George W. Bush administration.

Syria continues to go from bad to worse to terrible. The United States continues to follow events, not lead them. U.S. officials worry that greater violence, if not chaos, will follow the fall of Bashar al-Assad. They may be right, given the regime’s decades of misrule. But time matters.

The longer Assad clings to power, the worse the post-Assad period is likely to be; the longer violence will continue (and the more sectarian the struggle will become), the more Syrians will die, the more refugees will be created and the greater the opportunity for al-Qaeda to establish a terrorist beachhead in Syria.

What began as a peaceful civil resistance is increasingly degenerating into a sectarian war between Syria’s Sunnis and its Alawite Shiites that will almost surely spread beyond its borders. A war between Sunni and Shiite — backed by the Sunni Arab states on the one hand and Shiite Iran on the other — risks destabilizing not just Syria but also Iraq (which is still recovering from its own sectarian violence), Lebanon (which only recently regained its independence from Syrian occupation), Jordan (a long-standing U.S. ally) and even Turkey (worried about its restive Kurdish minority). Any of those developments would be a huge setback for U.S. allies and regional stability. It would squander a decade of U.S. investment of blood and treasure in the Middle East.

To avoid this looming debacle, the United States needs a much more active Syria policy. Necessary steps include:

●Accelerate efforts to help develop a more unified and inclusive Syrian opposition with an inclusive, cross-sectarian message. U.S. officials have made a significant effort and found it frustrating work, but there are signs of progress. Some Kurdish and Palestinian groups show signs of splitting from the Assad regime and moving to the opposition. Yet another inclusive, cross-sectarian statement was adopted by elements of the opposition last month.

●Increase efforts by U.S. intelligence officers to vet opposition groups. Identify those who support a unified Syrian opposition with an inclusive, cross-sectarian message and who are not affiliated with al-Qaeda or other terrorist groups. Help direct to such groups weapons provided by Saudi Arabia, Qatar, Turkey, the United States and European states. Include appropriate numbers of antiaircraft and antitank weapons so these groups can create no-fly/no-drive havens in which to train their forces and shelter at-risk civilians.

●Expand non-lethal support to these vetted opposition groups. Include food, water, cooking oil and fuel so they can provision themselves and take care of civilians in areas liberated from the Assad regime.

●Stop pursuing the Syrian issue in the U.N. Security Council. This would send a message to all Syrians, including the regime, that Russia and China can no longer protect Assad from the rest of the international community. The Security Council would have a role in helping the Syrian people achieve security and rebuild, but only after Assad goes.

●Build diplomatic support for this more active Syria policy among Turkey, other regional states and European allies. Their support is essential for successful execution and regional legitimacy. Reassure Iraqi and Lebanese leaders that the goal is an inclusive, cross-sectarian Syria that does not threaten Iraqi or Lebanese unity.

●Work closely with the Syrian opposition and regional allies to prepare for a post-Assad Syria. Include steps to secure Syria’s chemical weapons. A good place to start would be the U.S.-Turkey collaboration that Secretary of State Hillary Clinton announced in Ankara last week.

●Change the U.S. government’s public posture to show that we are leaning forward aggressively to hasten Assad’s departure.

●Along with the Syrian opposition, send messages both publicly and privately to the key pillars of the Assad regime:

Tell Syria’s minorities: You don’t need Assad to protect you; there is a place for you in the new Syria where you can feel secure and prosper.

Tell the Sunni business community: Assad’s clinging to power is all that prevents you from resuming your profitable trade with Turkey and other neighboring states.

Tell the Syrian military: Break with Assad now, and there is a place for you in the new Syria; go down with Assad, and you will be held responsible for his crimes.

This more active Syria policy does not involve U.S. airstrikes or “boots on the ground,” although the use of force should remain on the table to further pressure Assad. One hopes that U.S. military intervention will not be necessary. But that will be the case only if the United States provides appropriate numbers of antitank and antiaircraft weapons — despite the real risk that some weapons may fall into the wrong hands — so that U.S.-vetted opposition units can counter Assad’s stepped-up use of aircraft and helicopters against his own people. That way, when Assad falls, it will be the Syrian people who have toppled him. This is what Syrians clearly want. But they also want, need and deserve a little help from their friends.