THE FIGHTING in Gaza has served to obscure developments in another Middle East war that is far bloodier and more important to U.S. interests. In the last week, more than 700 fatalities have been reported in a single battle in Syria, as government troops have tried to retake a gas field seized by the Islamic State, the al-Qaeda entity that now controls much of eastern Syria and western Iraq. Fighting is also raging between regime and moderate rebel forces in the city of Aleppo and between the rebels and the Islamists in the suburbs of Damascus.

Among the stakes for the United States in this multi-sided conflict is whether the Iraqi state forged after the U.S. invasion can survive; whether the Islamic State will take root; whether the murderous Syrian regime of Bashar al-Assad will live on; and whether the region will become a base for terrorist attacks against the U.S. homeland. Senior Obama administration officials are sounding alarms about that last possibility: Attorney General Eric H. Holder Jr. recently said of the terrorist threat in Syria that “in some ways, it’s more frightening than anything I think I’ve seen as attorney general.” FBI Director James B. Comey said it “keeps me up at night.”

The Obama administration, however, appears to be doing little to address this crisis. Secretary of State John F. Kerry is camped out in Cairo in pursuit of a Gaza cease-fire, but no senior envoy is trying to work out a political formula that would unite moderate Syrian and Iraqi forces against the Islamic State. President Obama, who has devoted a large part of his schedule in recent weeks to political fundraising, had nothing to say about Syria or Iraq during recent appearances to discuss Gaza and Ukraine.

Even more disturbing are reports that the sole initiative undertaken by the administration on Syria since the collapse of an ill-conceived peace conference last winter is foundering. According to The Post’s David Ignatius and the Wall Street Journal, a promised $500 million effort to arm and train moderate rebels has emerged from the Pentagon as a pathetically underpowered scheme that would produce a force of just 2,300 over 18 months — and might not begin until next year.

Senior congressional staff consulted about the plan told the administration to go back to the drawing board. Rep. Adam Smith (D-Wash.), usually an administration ally, pointed out at a hearing that the White House was making little effort to sell its own policy. Meanwhile, the Free Syrian Army forces the administration proposes to support are steadily losing ground to the regime and the Islamists. There’s a real risk that by the time the program gets off the ground — if it ever does — there will be no units left to support.

It’s not easy at this late stage for the United States to intervene in Syria or Iraq in a way that would be constructive. But if one principle seems obvious, it is that moderate forces willing to fight the Islamic State should be aided — and quickly. Foremost among these are Syria’s secular rebels. The independent militia of Iraqi Kurdistan, which faces the Islamic State along a 900-mile front, is another clear candidate. Mr. Obama’s decision to stand back from Syria and Iraq has done much to create the present threat to the United States. Continued passivity will only make it worse.