MOSCOW - Russian President Vladimir Putin on Monday ordered a halt to an agreement with the United States on plutonium disposal, citing Washington's "unfriendly actions".

The deal, signed in 2000, was meant to allow both nuclear powers to dispose of weapons-grade plutonium from their defence programmes, a move seen as a key step in the disarmament process.

The two countries recommitted to the deal in 2010. The Kremlin indicated Monday that it would stick to the agreement if Washington lifts sanctions and ends other policies seen as unfriendly to Moscow.

Putin charged earlier this year that the United States was not honouring the deal by disposing of plutonium in a way that allowed it to retain its defence capabilities.

The suspension is symbolic of the breakdown in nuclear nonproliferation cooperation, an expert said.

The decree published Monday states that Russia is pulling out of the agreement "due to a drastic change in circumstances, the appearance of a threat to strategic stability due to unfriendly actions of the United States toward Russia".

It claimed that Washington was "unable" to carry out the terms of the agreement and that Moscow "must take urgent measures to defend Russian security".

Putin's spokesman Dmitry Peskov told journalists that Washington has not honoured the agreement and "Russia no longer thinks it possible to carry out the conditions of the agreement alone" due to "general tension" between the two countries.

"It's a symbolic gesture that demonstrates that the sides no longer cooperate in this sphere," said independent military expert Alexander Golts, adding that it was not the first agreement to be suspended in the non-proliferation sphere.

A bill submitted by Putin to parliament, which asked lawmakers to support the agreement's suspension, indicated that some quid pro quo could still keep the deal alive.

The bill said that the agreement could be reinstated if Washington moves US forces out of countries that became NATO members after 2000, ends "all sanctions" and compensates Moscow for the financial losses resulting from them.

Lawmakers can vote on the bill as early as Wednesday, when the State Duma convenes for the first time since being elected last month in a vote that saw the ruling United Russia party sweep some three quarters of the seats.

The US-Russian Plutonium Management and Disposition Agreement obliges Moscow and Washington to dispose of no less than 34 tonnes of weapon-grade plutonium by irradiating it or transforming it into so-called MOX (mixed oxide) fuel.

The building of a MOX fuel reprocessing plant was opposed in the United States in the wake of the 2011 Fukushima nuclear disaster in Japan over safety fears and high cost of the project, which is already billions of dollars over budget.

US energy officials have pushed for using another method of disposal, calling for plutonium to be mixed with other substances and stored underground, but Moscow argues that any method to dilute plutonium is reversable.

The two former Cold War adversaries are at loggerheads over a raft of issues including Ukraine, where Russia annexed Crimea in 2014 and supports pro-Moscow separatists, and the conflict in Syria.

The deal, signed in 2000 but which did not come into force until 2010, was being suspended due to "the emergence of a threat to strategic stability and as a result of unfriendly actions by the United States of America towards the Russian Federation", the preamble to the decree said.

It also said that Washington had failed "to ensure the implementation of its obligations to utilise surplus weapons-grade plutonium".

The 2010 agreement, signed by Russian Foreign Minister Sergei Lavrov and then-US Secretary of State Hillary Clinton, called on each side to dispose of 34 tonnes of plutonium by burning in nuclear reactors.

Clinton said at the time that that was enough material to make almost 17,000 nuclear weapons. Both sides then viewed the deal as a sign of increased cooperation between the two former adversaries towards a joint goal of nuclear non-proliferation.

"For quite a long time, Russia had been implementing it (the agreement) unilaterally," Kremlin spokesman Dmitry Peskov told a conference call with journalists on Monday.

"Now, taking into account this tension (in relations) in general ... the Russian side considers it impossible for the current state of things to last any longer."

Ties between Moscow and Washington plunged to freezing point over Crimea and Russian support for separatists in eastern Ukraine after protests in Kiev toppled pro-Russian President Viktor Yanukovich.

Washington led a campaign to impose Western economic sanctions on Russia for its role in the Ukraine crisis.

Relations soured further last year when Russia deployed its warplanes to an air base in Syria to provide support for Syrian President Bashar al-Assad's troops fighting rebels.

The rift has widened in recent weeks, with Moscow accusing Washington of not delivering on its promise to separate units of moderate Syrian opposition from "terrorists".

Huge cost overruns have also long been another threat to the project originally estimated at a total of $5.7 billion.