THROUGHOUT THE Cold War, the United States kept land-based missiles with nuclear warheads on alert and ready to launch in three to four minutes after the president gave the order. Every president of the missile age was briefed about the procedure: In the event of an impending attack, the decision to launch would have to be made in 13 minutes or less. The theory of deterrence was that the United States had to threaten certain and large-scale retaliation against the Soviet Union, and that meant being prepared to shoot fast.

When new presidents were briefed about how it worked, they found it unthinkable. “And we call ourselves the human race,” John F. Kennedy is said to have commented. Not the least of their worries was the prospect of incomplete or faulty warning — a bad signal from a satellite, perhaps, or a missile launched by accident or by rogue actors. There was never a real missile attack during the superpower arms race, but there were serious false alarms.

Today, two decades after the end of the Cold War, one-third of U.S. strategic forces, including almost all land-based missiles and some sea-based, are still on launch-ready alert. Recently, retired Gen. James Cartwright, a former vice chairman of the Joint Chiefs of Staff, called for rethinking this posture. Mr. Cartwright, a former commander of strategic forces, said in a report sponsored by the group Global Zero that the United States could stand down the missiles so that 24 to 72 hours would be needed to launch, what is known as “de-alerting.” There are different methods to carry this out, from software modifications to physically separating warheads from the missiles.

President Obama pledged in his 2008 campaign to work with Russia to take missiles off launch-ready alert status, and the idea was examined in the administration’s 2010 Nuclear Posture Review. One option was to de-alert the land-based missiles, but that was rejected on grounds that, in a crisis, there could be a destabilizing race to re-alert. Similarly, a proposal to de-alert the submarines, by keeping more at port, was also rejected. The published document said that launch-ready status “should be maintained for the present.”

In the coming weeks, the president is expected to sign off on instructions to the military to implement the posture review. No change is anticipated in alert levels. Gen. C. Robert Kehler, the current commander of U.S. Strategic Command, said recently that he is reluctant to de-alert missiles because it would be hard to verify if some adversary posed a risk of surprise attack. We agree that verification is difficult, but that is all the more reason to look for ways to make it work.

The reason the United States maintains a prompt-launch posture today is because Russia does also. China does not keep weapons on launch-ready alert. The United States and Russia are no longer enemies; the chance of nuclear war or surprise attack is nearly zero. A small step toward reducing the danger was taken in 1994, when Russia and the United States agreed to aim nuclear missiles at the open oceans, or at nothing. But this did not resolve the time pressures on a president, nor relax the launch-on-warning posture that still prevails.

Clearly, there won’t be any arms control negotiations with Russia this election year. But this is a complex problem that could benefit from careful preparation. Mr. Obama has declared his commitment “to seek the peace and security of a world without nuclear weapons.” A good start would be to give himself and mankind some breathing room. Today, the United States and Russia have as many as 1,800 warheads on alert at any given time. This is overkill and unnecessary so long after the Cold War has ended. We think that both countries should ease off the alert status for strategic forces.