THE OBAMA administration has been careful to say that some matters of bilateral interest with Russia can remain on the table despite the confrontation over Russia’s seizure of Crimea and subversion in eastern Ukraine. One such area still under discussion has been the claim made this year by the United States that Russia violated the 1987 Intermediate-Range Nuclear Forces treaty, which eliminated an entire class of nuclear weapons and delivery vehicles in Europe. Russia claims the United States also has violated the treaty. Yet this conversation is going nowhere. The treaty is valuable to both nations, and Russia, in particular, ought not to slow-walk resolution of a nettlesome disagreement.

The treaty, which entered into force in 1988, required the elimination of all the approximately 800 U.S. and 1,800 Soviet ground-launched missiles with maximum ranges between 500 and 5,500 kilometers, as well as their launchers and associated support equipment. It was a Cold War landmark that reversed a dangerous period in the late 1970s and early 1980s when both sides were deploying nuclear-armed missiles in Europe aimed at each other. The missiles were eliminated by 1991. The treaty barred possession, production or flight tests of such weapons.

The administration says that Russia has now broken the treaty by flight-testing a ground-launched cruise missile. While details remain classified, our sources say it was a flight test of a new ground-launched cruise missile that is not yet in serial production. Certainly, a single test is not the same as full-scale production, but a violation is a violation, and it should be taken seriously.

The administration charged treaty noncompliance in July, and a high-level meeting was held Sept. 11 in Moscow, but without result. On Dec. 10, Brian McKeon, principal deputy undersecretary of defense, told a House hearing, “Unfortunately, Russia has not been forthcoming with any information, nor has it acknowledged the existence of such a noncompliant cruise missile.” Russia’s response has been to kick up dust, claiming the United States is violating the treaty, charges that the administration describes as baseless.

Mr. McKeon disclosed that a Pentagon assessment had concluded the cruise missile in question would be a military threat to the United States if deployed, and he raised a number of possible countermeasures, including military responses, such as erecting new defenses against the missile or deploying countervailing U.S. missiles. Such moves would also violate the treaty.

This was a useful trial balloon — and it ought to focus thinking in the Kremlin. Rather than restart an arms race in Europe, it would make a lot more sense to resolve this complaint now. But the evident lack of progress suggests that the crisis over Ukraine and renewed hostility between Washington and Moscow is spilling over into many other areas, including this one. Russia’s destructive behavior in Ukraine has badly shaken European security. Carelessly ditching the Intermediate-Range Nuclear Forces treaty would be another shock, and Russia ought to avoid it.