WE DETECTED a whiff of complacency when President Obama declared, in the State of the Union address on Tuesday, that $2.5 trillion in 10-year budget savings achieved so far put the nation “more than halfway towards the goal of $4 trillion that economists say we need to stabilize our finances.” The president added: “We need to finish the job.”

Deficit reduction is still more urgent than these words imply, recent favorable trends notwithstanding. The U.S. might be able to get to the $4 trillion mark with relatively modest additional measures — but “the job” of truly stabilizing America’s long-term finances would still be anything but finished.

The president’s view tracks with analyses by the Center on Budget and Policy Priorities (CBPP), the distinguished left-of-center Washington think tank. The CBPP, relying on economic and technical assumptions from the nonpartisan Congressional Budget Office (CBO), has argued that $1.5 trillion in additional deficit reduction over the next decade would help get the federal debt to 73 percent of gross domestic product (GDP) by 2018 and keep it there through 2023.

Yet a debt-to-GDP ratio of 73 percent would be extremely high by historical standards, leaving little “fiscal space” below the 90 percent ratio economists often cite as a drag to growth. What’s more, even if the government were to achieve the “stable” debt level Mr. Obama envisions, demographic changes will push health-care spending higher soon thereafter, and, with it, the debt. Even the CBPP does not claim that we can save another $1.5 trillion and call it quits. The latest version of its analysis, published last week, acknowledges that the 73-percent-of-GDP scenario represents “the minimum appropriate budget policy.”

Now, not later, is the time to put the debt on a downward trajectory. The sudden, blunt-force spending shrinkage embodied in the “sequester” scheduled to take effect on March 1 might do more harm than good. What’s needed instead is a serious, sustained effort to reform the entitlements that increasingly dominate the federal budget: especially Medicare and Social Security, including the latter’s fast-growing disability program.

A comprehensive structural overhaul, whether by way of the GOP plan for “premium support” in Medicare or other means, is, to be sure, a bridge too far politically at this point. Also, Medicare’s growth has already slowed on account of broader but unexpected and poorly understood changes in health-care economics. But that windfall represents a respite, not a solution.

As we have noted previously, policy wonks of both parties have developed proposals to save more than $450 billion from Medicare over 10 years. One such idea, higher premiums for well-off Medicare recipients, was included in Mr. Obama’s speech. But there are many more, including overhauling Medicare’s hodgepodge of cost-sharing requirements, which promote inefficient “Medigap” coverage. (Savings, according to CBO: $92.5 billion over 10 years.)

In that regard Mr. Obama’s mention of “modest” reforms was ambiguous. An attempt to prepare the public for big changes by casting them as relatively bearable — as they, indeed, are? Or a new excuse for can-kicking? We hope that he meant the former.

If the president is afraid to go too far, he might end up not going far enough.