Russia and the U.S. will each dispose of 34 metric tons of excess weapon-grade plutonium, Russian Foreign Minister Sergei Lavrov said on Tuesday.

Lavrov and U.S. Secretary of State Hillary Clinton signed Tuesday a protocol to amend the U.S.-Russian 2000 agreement on eliminating excess weapon-grade plutonium from defense programs.

"We will spend up to $2.5 billion to dispose of 34 metric tons of our [excess weapon-grade] plutonium in line with this protocol, the U.S. side will provide some $400 million as its contribution to our program," Lavrov told journalists in Washington, where a 47-nation nuclear security summit is under way.

The U.S. State Department earlier said in a statement the signing was a "major and essential step toward enabling full implementation of our two countries' obligation to safely and transparently dispose of such excess weapon-grade plutonium, enough material for several thousand nuclear weapons."

"The signing also signifies our commitment to making arms reductions irreversible and to reducing the danger of this material ever falling into the hands of terrorists," the statement added.

Last week in Prague U.S. President Barack Obama and Russian President Dmitry Medvedev signed a new strategic arms reduction treaty. It still has to be ratified by the Russian parliament and the U.S. Congress.

The two countries, which possess about 90% of global arsenals of nuclear weapons, agreed in Prague to reduce the number of nuclear warheads to 1,550 on each side and the number of deployed and non-deployed delivery vehicles to 800 on each side.