Russia has told the US it has "temporarily" suspended on-site inspections of its strategic nuclear weapons, under an arms control treaty known as New START.
The Russian foreign ministry said the US was seeking advantages and had deprived Russia of the right to carry out inspections on US territory.
It said US sanctions imposed on Russia over Ukraine had changed conditions between the countries.
The treaty came into force in 2011.
It is the last remaining arms reduction agreement between the former Cold War rivals. It caps at 1,550 the number of long-range nuclear warheads that each country can deploy.
The ministry said the suspension was allowed under the treaty terms "in exceptional circumstances".
The suspension comes a week after US President Joe Biden said he was ready to work on a new nuclear arms deal with President Vladimir Putin. The current one will expire in 2026.
The ministry accused the US of ignoring "existing realities" such as "the suspension of normal" air links.
New START followed years of arms reduction talks between the US and former USSR, aimed at preventing nuclear war.
Russia's invasion of Ukraine in February sparked hostile rhetoric on both sides, including warnings that the conflict could escalate into a third world war.
Some commentators on Russian state media have boasted about Moscow's nuclear arsenal in the context of current tensions with Nato.