The United States and Russia signed an update to a 2000 agreement Tuesday intended to eliminate weapons-grade plutonium from their military programs.
Secretary of State Hillary Rodham Clinton and Russian Foreign Minister Sergei Lavrov signed the new protocol amending the earlier agreement at the nuclear security summit involving 47 countries.
Clinton said the agreement commits each country to "irreversibly and transparently" dispose of at least 34 metric tons of weapons-grade plutonium.
She said the total amount of material involved is enough for 17,000 nuclear weapons.
Both Clinton and Lavrov said the agreement prevents any future military use of the plutonium.