Russia's decision to suspend the New Start nuclear arms treaty has been criticized by US Vice President Joe Biden as a major error.
In his yearly speech to the nation on Tuesday, President Vladimir Putin announced the move.
The agreement, which was signed in 2010, gives each country the authority to inspect the other's arsenal while putting a cap on the number of nuclear warheads that the US and Russia are allowed to possess.
In Poland, Vice President Biden met with a significant group of NATO allies.
Nearly a year after it began, the group of eastern European nations known as the Bucharest Nine reiterated their opposition to Russia's invasion of Ukraine.
On Wednesday, both houses of Russia's parliament formally approved Putin's decision to halt participation in the nuclear treaty.
However, the Russian foreign ministry later declared that Moscow would uphold the restrictions of the New Start treaty in a "responsible manner".
Russia will continue to adhere to the limitations on nuclear delivery systems, which include missiles and strategic bomber aircraft, a senior military official told the lower house of the Russian parliament.
The New Start treaty, which was signed in 2010 by Dmitry Medvedev and Barack Obama, was intended to stop nuclear war. It gives each nation the authority to inspect the other while limiting the number of strategic nuclear warheads that both sides can deploy.
Although the Covid pandemic interfered with weapons inspections, the agreement entered into force in 2011 and was extended ten years later.
The cap on long-range nuclear warheads is 1,550 for each side, which is less than the previous Start agreement.
Nearly all of the nuclear weapons in the world are owned by the two former Cold War adversaries collectively. Despite hostile rhetoric from both sides during the conflict in Ukraine, Russia had previously stated that it wanted to keep the treaty in effect.
Mr. Biden said suspending New Start was a "big mistake" and reaffirmed the US commitment to the military alliance in remarks made prior to the meeting with leaders of the Bucharest Nine nations, which make up Nato's eastern flank.
"The United States has sworn to uphold Article 5 as a sacred obligation. We will defend NATO in its entirety, he declared. According to Article 5, an attack on one member state triggers a joint defense of all member states.
He declared them to be the "front line of our collective defense" in front of the leaders present. The group vowed to increase NATO's military presence on their soil in a joint statement following the meeting.
Russia claims that NATO, which could soon welcome Sweden and Finland as members, poses an existential threat.
Putin claimed that Russia was fighting in Ukraine for its "historical" lands while speaking at a rally in Moscow to commemorate one year of the conflict.
He stated: "I just heard from the top military leadership of the nation that a battle is ongoing right now, for our historical lands, for our people.
He had previously met Wang Yi, China's top diplomat, in Moscow, where he had stated that cooperation with Beijing was "very important to stabilize the international situation.".
Mr. Wang declared that Beijing was prepared to deepen its alliance with Moscow and that external pressure would have no bearing on their relationship.
