Russian President Vladimir Putin on Monday suspended a deal with the United States to dispose of excess supplies of weapons-grade plutonium, citing a large deterioration in bilateral ties.
Russia will not proceed with the programme amid recent "threats to strategic stability as a result of unfriendly US actions towards Russia," Putin said in his order, posted on the government's legal information website.
The White House called Russia's decision to unilaterally withdraw from the agreement "disappointing."
The agreement had shown the US and Russia had made non-proliferation a priority.
"The United States is interested in limiting proliferation and trying to reduce the risk associated with potential nuclear terrorism," spokesman Josh Earnest said.
Putin also accused the United States of failing to fulfill its half of the deal. The pact was agreed in 2000 to dispose of dozens of tons of plutonium, enough for thousands of nuclear weapons.
Earnest however stressed the US has upheld the agreement since it took effect in 2011 and "would like to see the Russians continue to do the same thing."
Meanwhile, Putin submitted a bill to parliament to set preconditions for the programme to be resumed, including a reduction of US military infrastructure in certain NATO states, as well as the removal of US sanctions against Russia.
Relations between the US and Russia have deteriorated amid Russian involvement in Syria as well as Ukraine, and the State Department on Monday broke off diplomatic engagement with Russia on Syria amid a spiral of escalating violence.
"We've obviously been quite disappointed about a range of Russian decisions however both inside of Syria but also in Ukraine. And unfortunately the announcement about the Plutonium Management and Disposition Agreement is more in line with those kinds of decisions that have only deepened Russia's isolation in the international community," Earnest said.