Russia’s lower house of parliament has denounced an agreement with the US on the disposition of its vast stockpile of weapons-grade plutonium left over from thousands of Cold War nuclear warheads.

The State Duma, the lower house of the Federal Assembly of Russia, said in a statement on Wednesday that the Plutonium Management and Disposition Agreement was denounced by lawmakers after a bill on the matter was adopted during the parliament’s plenary session.

“The decision is made solely in the interests of the Russian Federation and its citizens. We are denouncing an agreement that should have been terminated long ago,” State Duma Speaker Vyacheslav Volodin was quoted as saying in the statement about the bill’s adoption.

He also thanked the Russian Foreign Ministry, particularly for leading the work in this regard.

“Those who want to exploit Russia must understand this will not happen. We have a strong president, a responsible parliament, and an effective government,” he added.

Maintaining Russia's obligations under the Plutonium Management and Disposition Agreement with the United States is no longer acceptable, TASS said, citing Deputy Foreign Minister Sergei Ryabkov.

"The United States has taken a number of new anti-Russian steps that fundamentally change the strategic balance that prevailed at the time of the Agreement and create additional threats to strategic stability," a Russian note on the legislation withdrawing Moscow from the pact said.

Russian Deputy Foreign Minister Sergey Ryabkov, who also attended the plenary session, explained to lawmakers that the reason for the suspension of the deal was a “fundamental change in circumstances”, including Washington’s implementation of sanctions on Moscow and NATO’s eastward expansion.

He was further quoted as saying that the Russian side had formulated conditions for the renewal of the agreement, but that none of these conditions can currently be met.

“And in this situation, the process of terminating cooperation with the Americans under the agreement, even from a formal standpoint, simply seems natural,” he added.

Under the Plutonium Management and Disposition Agreement, signed in 2000, both Moscow and Washington each committed to disposing of 34 tonnes of weapons-grade plutonium.

The deal was amended in 2010 and entered into force a year later.

In October 2016, Russian President Vladimir Putin signed a presidential decree suspending Moscow’s implementation of the deal, citing multiple factors, including what it described as the “emergence of a threat to strategic stability as a result of the unfriendly actions of the United States of America toward the Russian Federation.”