A year ago, when Syrian deaths were estimated at 7,000 and al-Qaida had yet to establish a foothold, President Obama objected to proposals for U.S. intervention on the grounds that it could lead to the militarization of the conflict or play into extremists’ hands.

Today, the extremists are ascendant, fighting between President Bashar Assad’s forces and the rebels is spilling over into Iraq and Lebanon, and the estimated death toll tops 70,000. Yet the administration persists in its wishful thinking and defeatist excuse-making. It has announced plans to channel small amounts of nonlethal aid to some rebel forces on the expectation that this will “change Assad’s calculations” and prompt him to step down.

There are reports of a modest covert operation to train some rebels. But the administration refuses to encourage the establishment of a full-fledged alternative government on the grounds that this might interfere with a moribund U.N. plan for negotiations.

As from the start, it’s relatively easy for Syrian realists to see where the conflict is going. Most likely, as the regime slowly loses ground to the rebels, Syria will crack into pieces controlled by rival authorities — including a regime remnant in Damascus or along the Mediterranean coast, backed by Iran, and an al-Qaida-controlled zone along the border with Iraq. Fighting along sectarian lines, and between extremist and moderate Sunnis, will continue to spread into Lebanon and Iraq. Eventually the regime may resort to using chemical or biological weapons or attempt to transfer them to its Lebanese or Iranian allies.

The means to prevent this implosion are the same that could have stopped the ignition of the civil war: aggressive intervention by the United States and its allies to protect the opposition and civilians. This would not require ground troops, only more training and the supply of heavy weapons to the rebels, and airstrikes to eliminate the regime’s warplanes, missiles and, if necessary, chemical weapons. The recognition of an alternative government led by the civilian Syrian National Coalition would send the message to wavering regime supporters that it was time to defect and would help to isolate al-Qaida before it is too late.

Several of President Obama’s top advisers pressed him to consider such measures six months ago. Key U.S. allies, including Britain, France, Turkey, Saudi Arabia and Israel, have quietly pleaded with the White House to act. It has been 18 months since President Obama first claimed that time was running out for the Assad regime. Now it is running out for him. His continued refusal to intervene in Syria will invite an even greater catastrophe that will indelibly stain his presidency.