Abstract
The crisis in Ukraine probably has ruined prospects for another formal Russian-U.S. arms control agreement during the Obama administration’s second term. Even before the crisis over Crimea, Russian and U.S. negotiators differed sharply on their preferred outcomes for reducing their strategic nuclear forces further, eliminating or consolidating nonstrategic nuclear weapons in Europe, constraining national and theater strategic defenses, or renewing conventional arms limitations in Europe.
For countering nuclear weapons proliferation to states and to nonstate actors, the prospects are somewhat better, given mutual Russian and U.S. concerns in that area. The two countries continue to cooperate to constrain the nuclear weapons potential of Iran and North Korea, although even their combined influence in Tehran and Pyongyang is small. Given the historically pre-eminent roles of Russia and the United States in supplying global nuclear materials and technologies and their large stockpiles of nuclear materials and weapons, their nonproliferation collaboration is perhaps even more important for denying terrorists access to weapons of mass destruction (WMD), especially nuclear weapons.
 
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