Russian President Vladimir Putin suspended an agreement with the U.S. over the disposal of surplus weapons-grade plutonium, making it obvious to everyone that the bilateral relations between these two countries are worsening.
In a decree, Putin accused the US of creating "a threat to strategic stability, as a result of unfriendly actions" towards Russia.
He also set pre-conditions for the US for the deal to be resumed.
Under the 2000 deal, each country is supposed to get rid of 34 tons of plutonium by burning it in reactors as part of cuts to nuclear forces.
The US state department said the combined 68 tons of plutonium was "enough material for approximately 17,000 nuclear weapons". Both countries had reconfirmed the deal in 2010.
The state-run Tass News Agency reported the agreement was suspended because of "unfriendly" acts by Washington.
The Obama and Putin administrations have been at increasing odds over several issues, but the tensions between the two sides over the five-year-old civil war in Syria has seen a recent marked increase in hostile diplomatic behavior, according to CBS News.
Moscow: We fulfilled our duties
In Monday's decree, Putin said Russia had to take "urgent measures to defend the security of the Russian Federation".
Back in April, the Russian president said the US was failing to fulfil its obligations to destroy plutonium. Instead, he said, the US reprocessing plutonium to be extracted and used again in nuclear weapons.
Both counties had the agreement to build special facilities for disposal of the surplus plutonium.
"We fulfilled out duties, we built that enterprise. But our American partners did not," Vladimir Putin said.
The US rejected that claim, insisting that its disposal method did not violate the agreement.
Tensions between Moscow and Washington is even bigger since last month because of Russia's bombing campaign in Syria, which U.S have described as a "war crime".
Russian planes are to help Syrian government to hit rebel groups, some of which are supported by the US and its other allies.
