Through the Co-operative Threat Reduction program, the Department of Defense provides equipment, services, and technical advice to Russia, Belarus, Kazakhstan, and Ukraine to assist them in eliminating (or in the case of Russia, reducing) the weapons of mass destruction remaining from the Soviet era, preventing proliferation, and dismantling the associated infrastructure or transforming portions of it to engage in peaceful civilian activities.
The U.S. objectives in the CTR program as established by Congress are to cooperate with the Newly Independent States (NIS) of the former Soviet Union to:
* Destroy nuclear, chemical, and other weapons of mass destruction;
* Transport, store, disable, and safeguard weapons in connection with their destruction;
* Establish verifiable safeguards against proliferation of such weapons;
* Prevent diversion of weapons-related expertise;
* Facilitate demilitarization of defense industries and conversion of military capabilities and technologies; and
* Expand defense and military contacts between the United States and the NIS.
These objectives are inextricably linked with each other. Meeting the objective of safeguarding nuclear weapons in Russia, for example, would also help prevent proliferation, a growing concern in light of ongoing reports of nuclear material smuggling.
CTR has faced significant challenges, not least of which is a level of corruption and non-cooperation that makes success in Russia very difficult.
You can read more about the history of the program here.