Editor's note:

The U.S.-Russia nuclear arms treaty, New START, is set to expire in February 2021. Little progress was made during the summer and it was unclear if the two countries would reach an agreement. However, a breakthrough has given the arms control treaty a new lease on life, albeit with a lot of questions, writes Steven Pifer. This piece originally published by the Freeman Spogli Institute’s Center for International Security and Cooperation at Stanford University.

While concern had grown over the past several weeks about a breakdown in U.S.-Russian arms control, it appears the 2010 New Strategic Arms Reduction Treaty and nuclear arms control more broadly may have a new lease on life, albeit with lots of questions.

Washington’s negotiation with Moscow on New START hit a roadblock on October 16. President Putin said Russia would agree to a one-year extension, which U.S. negotiators had proposed instead of five years, but without the conditions sought by the American side. National Security Advisor O’Brien summarily rejected the Russian position because it ignored the U.S. demand for a freeze on all nuclear warhead numbers.

Things changed recently. The Russians announced that they would agree to a one-year extension of New START and said they are “ready to assume a political obligation together with the United States to freeze the sides’ existing arsenals of nuclear warheads during this period.” The Russian statement added that this presumed no additional U.S. conditions. The Department of State spokesperson quickly and positively reacted, saying U.S. negotiators are “prepared to meet immediately to finalize a verifiable agreement.”

New START constrains U.S. and Russian strategic nuclear forces to their lowest levels since the 1960s. However, when it comes to nuclear warheads as opposed to delivery systems, the treaty limits only “deployed” strategic warheads—that is, warheads on deployed intercontinental ballistic missiles (ICBMs) or submarine-launched ballistic missiles (SLBMs). The treaty does not cover reserve strategic warheads or any non-strategic (tactical) nuclear weapons.

If Russian acceptance of a one-year freeze means that the Trump administration has succeeded in persuading Moscow to negotiate a treaty limiting all U.S. and Russian nuclear weapons, that is a commendable breakthrough. Indeed, a treaty covering all the two sides’ nuclear arms has long seemed the logical next step after New START (President Obama proposed such a negotiation in 2010).

Questions remain, however. The Russian statement indicates that Moscow is ready to undertake, as a political obligation, a one-year freeze on nuclear warhead numbers. It remains unclear whether Russian officials, beyond that freeze, are prepared to negotiate a legally-binding and verifiable treaty constraining all nuclear warheads that would be in effect for a number of years (New START is in force for 10 years, with the possibility of its extension for an additional five years).

In the past, Russian officials have made a variety of demands for negotiating such a treaty. They made withdrawal of U.S. non-strategic nuclear weapons from Europe (about 150 nuclear gravity bombs) a precondition. They also insisted that the United States had to address Russian concerns about long-range, precision-guided conventional strike systems and missile defense.

When it comes to negotiation of a treaty, not just a freeze, will Russian officials maintain these demands? If they do, a complex negotiation will become even more difficult. The Trump administration has been adamant, for example, that it will not agree to constraints on missile defense.

Verification presents another stiff challenge. New START provides procedures for counting strategic warheads on ICBMs and SLBMs. However, when a warhead is taken off of an ICBM or SLBM and placed in storage, for all intents and purposes, it disappears as far as New START is concerned.

The State Department spokesperson’s statement about finalizing a “verifiable agreement” left uncertain whether it referred to the treaty to be negotiated or the freeze. U.S. arms control negotiator Billingslea later said the freeze would require measures for effective verification. Yesterday’s statement from Moscow, however, was silent on verification.

Provisions to allow effective verification of all nuclear warhead numbers will prove far more intrusive than anything the U.S. and Russian militaries have accepted to date. The Trump administration has expressed interest in a portal system, which would provide for monitoring of things that leave or enter a production facility. However, accounting for the total number of warheads on each side presumably would require monitoring systems at, and perhaps access into, storage sites for nuclear weapons. These are among the most sensitive facilities that either side has. Negotiating that kind of verification will prove an arduous process and take a time—and may require the development of new technologies for monitoring purposes.

Finally, Mr. Billingslea said that, while the freeze would apply to the U.S. and Russian nuclear arsenals, the treaty to be negotiated would be trilateral and include China. Beijing consistently has rejected taking part in a trilateral arms treaty.

So, it appears that U.S. and Russian negotiators still have issues to resolve.

Irrespective of the freeze, New START is worth saving and extending to 2026 (the treaty’s terms provide that there could be multiple extensions). Extension to 2026 would mean five more years of limits on Russian strategic nuclear forces. It would mean five more years of information about those forces provided by the treaty’s verification measures, including data exchanges, notifications and on-site inspections. And extending the treaty would require no change in U.S. strategic modernization plans, as those plans were designed to fit within the treaty’s limits.

One last observation: New START requires that, if a side wishes to withdraw from the treaty, it must give the other three months’ notice before doing so. It is now October 21, which means that, if negotiations with the Russians do not go well and the Trump administration were to give notice, the United States could not actually withdraw from the treaty until after January 20, 2021—when Donald Trump will be starting his second term or Joe Biden will have become the 46th U.S. president. Mr. Biden is on record as supporting New START’s extension for five years, with no conditions.