On 16 September 2010, the IAEA´s Director General Yukiya Amano received a jointly signed letter from the Russian Minister for Foreign Affairs, Sergey Lavrov, and the U.S. Secretary of State, Hillary Rodham Clinton, requesting that the IAEA undertake "an important verification role under the amended Agreement between the Government of the Russian Federation and the Government of the United States of America Concerning the Management and Disposition of Plutonium Designated as No Longer Required for Defense Purposes and Related Cooperation".
The amended Agreement between the Russian Federation and United States creates a "framework for cooperation and establishes the infrastructure for disposition of weapon-grade plutonium designated as no longer required for each side´s defense programs, initially 34 metric tons each or enough for thousands of nuclear weapons."
The disposition agreement calls on the Russian Federation and the United States to undertake "all necessary steps to conclude appropriate agreements with the IAEA to allow it to implement verification measures with respect to each Party´s disposition program" and to prepare "the necessary legally-binding verification agreements in 2011".
The full text of the letter can be accessed here [pdf].