So it serves American interests to extend the treaty. At the same time, we need to tackle the problems that the administration has highlighted. The agreement can be extended for five years, or until it is superseded by a new treaty. Success in a new negotiation should be something that we all welcome.

How do we treat new Russian weapons? Here, too, the pact can help. Some of the Russian systems, such as the new heavy missile, meet the definition of an ICBM under the treaty; they would therefore fall under it without any additional negotiation. The new boost-glide missile system might also be brought under the treaty, since it is launched on a version of an existing Russian ICBM. The Russians have all but said this system will be accountable under the treaty.

But if New START is not extended, Russia would be able to field both the heavy missile and boost-glide system without any constraints.

New systems like the Burevestnik, a nuclear-propelled cruise missile, would take more work, since they do not fit the category of missiles defined in the treaty. Here it might be worth a straightforward discussion with the Russians: Do they really need the system? As the radioactive explosion near Arkhangelsk in August showed, the missile will be dangerous to operate and dangerous to deploy — both for the experts handling it and the public living near its bases.

The system is not needed. For more than 30 years, since Ronald Reagan’s Star Wars program was announced, the Soviets and Russians have poured money into ensuring that their missiles can penetrate defenses against incoming missiles. Chaff, decoys, maneuvering re-entry vehicles: Russia is best in class in all of these systems to keep I CBMs on course to their targets. The rationale for the new missile is that it would succeed if the ICBMs fail, but that is unlikely. This makes the Burevestnik an elaborate redundancy, and dangerous in the bargain.

Straightforward discussion may also be the way to get the Chinese to play. In the 50 years since the United States and the Soviet Union, later Russia, have been negotiating about bilateral nuclear restraint, the Chinese have never been part of the process. They have expressed restraint through a national no-first-use policy and by keeping their nuclear arsenal small. But with their continuing nuclear modernization, we need to wonder — is China moving beyond assuring a second strike if hit first? Is it striving for parity with the United States and Russia?

Seeking some clarity about Chinese intentions should be a first order of business. The Chinese are not allergic to all negotiated measures. They are signatories of the Nuclear Nonproliferation Treaty and Comprehensive Test Ban Treaty, and they have cooperated to prevent proliferation — for example, working with the United States on nuclear security in their port complexes and elsewhere to prevent nuclear terrorism during the Beijing Olympics in 2008.