The Obama administration’s emerging support for rebels in Syria is a welcome move, although it comes too late to help the estimated 70,000 people who have died over two years as President Bashar Assad wages a desperate fight to maintain his dictatorial grip on the country.

The administration’s hesitant approach to the Syrian conflict has been based in large part on fear of the unknown. Unlike in Libya, officials knew little about the insurgents fighting Assad. They feared that arms sent to the rebels would wind up in the hands of anti-American Islamist terrorists.

Countries in the region with the greatest self-interest in getting rid of the corrupt Assad regime — mainly, Saudi Arabia — were unwilling to act, hoping the U.S. would take care of the problem for them.

That did not suit President Obama’s policy, which favors acting in tandem with regional allies rather than taking action unilaterally. Nor did greater involvement in a Middle East war fit the mood of an American public weary of overseas military commitments.

But those arguments can no longer be sustained in view of the Syrian regime’s increasingly brutal and cowardly tactics, such as the deliberate targeting of hospitals and medical professionals, and Assad’s near-certain defeat.

Even the cautious Saudis have finally been moved to act, reportedly financing a large weapons shipment to nationalist and secular factions within the rebel movement in an effort to stop the slaughter of civilians.

The fear that Islamist factions will win the upper hand in a post-Assad regime remains real, but the Obama administration can’t afford to wait any longer. The U.S. is compelled to act for humanitarian reasons and because the absence of American assistance to secular groups only weakens pro-Western forces as the noose begins to tighten on Assad. Further hesitation undercuts the administration’s influence on future leaders of the country and works against U.S. interests.

Secretary of State John Kerry said Wednesday “the opposition needs more help,” signaling that the administration is moving toward a major policy shift. But that still leaves American policy far too vague. It’s time for the administration to stop mincing words and speak clearly about U.S. willingness to provide direct assistance, including military aid, to Syrian insurgents.

When Mr. Kerry attends an international conference on Syria in Rome on Thursday, he must speak clearly in favor of American action to tip the scales at this decisive moment. It is not necessary to commit American forces to the conflict in order to make a difference. But at this stage it would be inexcusable to refuse to act to put an end to the mounting death toll and the suffering of the Syrian people.