Every four years the White House issues a “nuclear posture review.” That may sound like an anachronism. It isn’t. In a world where the United States and Russia still have more than 20,000 nuclear weapons  and Iran, North Korea and others have seemingly unquenchable nuclear appetites  what the United States says about its arsenal matters enormously.

President Obama’s review was due to Congress in December. That has been delayed, in part because of administration infighting. The president needs to get this right. It is his chance to finally jettison cold war doctrine and bolster America’s credibility as it presses to rein in Iran, North Korea and other proliferators.

Mr. Obama has already committed rhetorically to the vision of a world without nuclear weapons. But we are concerned that some of his advisers, especially at the Pentagon, are resisting his bold ambitions. He needs to stick with the ideas he articulated in his campaign and in speeches last year in Prague and at the United Nations.

These are some of the important questions the posture review must address:

THEIR PURPOSE: Current doctrine gives nuclear weapons a “critical role” in defending the United States and its allies. And it suggests they could be used against foes wielding chemical, biological or even conventional forces  not just nuclear arms. Mr. Obama’s aides have proposed changing that to say that the “primary” purpose of nuclear weapons is to deter a nuclear attack against the United States or its allies. This still invites questions about whether Washington values  and might use  nuclear forces against non-nuclear targets.