TESTIMONY BY senior U.S. officials to Congress this week about Syria has made one thing clear: The Obama administration has yet to face up to its own assessment of what is happening in that strategic Arab country.

For months President Obama has been declaring that the fall of dictator Bashar al-Assad is “inevitable” or “a question of when,” as he put it Tuesday. But Marine Gen. James Mattis, the head of U.S. Central Command, told the Senate Armed Services Committee the same day that Mr. Assad is “gaining physical momentum” in his assault on his rebellious population. “He’s going to be there for some time because I think he will continue to employ heavier and heavier weapons,” Gen. Mattis said. “It will get worse before it gets better.”

Mr. Obama also derided suggestions that the United States should intervene militarily. Among other things, he said “we’ve got to think through . . . what’s critical for U.S. security interests.” But Gen. Mattis said that if the Assad regime were to collapse, “it’ll be the biggest strategic setback for Iran in 20 years.”

Testifying to the same committee on Wednesday, Defense Secretary Leon Panetta agreed with that judgment. He also said,“I don’t think there’s any question that we’re experiencing mass atrocities” in Syria. That came after Sen. John McCain (R-Ariz.) cited Mr. Obama’s presidential directive, which says that “the prevention of mass atrocities is a core national security interest of the United States.”

To sum up: According to the administration, it is a vital U.S. interest to prevent crimes against humanity like those underway in Homs and other Syrian cities; the fall of Mr. Assad would be a major blow to the greatest strategic adversary of the United States in the Middle East; and, at least for the moment, the regime is winning rather than losing its war to stay in power. Yet the U.S. response remains limited to diplomatic and humanitarian measures that are unlikely to stop further massacres.

By the administration’s own logic, more assertive action is unavoidable. At Wednesday’s hearing, Mr. Panetta and Joint Chiefs of Staff Chairman Gen. Martin Dempsey were pressed by Mr. McCain and Sens. Joseph I. Lieberman (I-Conn.) and Lindsey O. Graham (R-S.C.), who have joined in calling for the creation of a coalition to carry out airstrikes on the Assad forces. The senators, and some governments in the region, favor creating a protected zone inside Syria where refugees could gather and opposition forces could organize.

Mr. Panetta said that military options could be considered by NATO. But Gen. Dempsey warned that taking out Syrian air defenses would take “an extended period of time and a great number of aircraft”; he questioned whether the opposition was coherent enough to be helped. Mr. Panetta echoed Mr. Obama in protesting that “we have to build a multilateral coalition” before taking stronger action.

These are not frivolous objections. But Gen. Dempsey also reported that the military mission of stopping the Assad forces could be accomplished. And the best way to ensure that extremists do not hijack the Syrian opposition is for the United States and its allies to identify and support more moderate elements.

As for building an international coalition for more forceful action, that historically has been the responsibility of the United States and its president. If Mr. Obama does not lead on Syria, there will be no international consensus — and an outcome that meets U.S. interests will be anything but inevitable.