By Humeyra Pamuk
WASHINGTON (Reuters) -The United States on Tuesday accused Russia of violating the New START Treaty, the last major pillar of post-Cold War nuclear arms control between the two countries, saying Moscow was refusing to allow inspection activities on its territory.
The treaty came into force in 2011 and was extended in 2021 for five more years. It caps the number of strategic nuclear warheads that the United States and Russia can deploy, and the deployment of land- and submarine-based missiles and bombers to deliver them.
The two countries, which during the Cold War were constrained by a tangle of arms control agreements, still account together for about 90% of the world's nuclear warheads.
Washington has been eager to preserve the treaty but ties with Moscow are the worst in decades over Russia's invasion of Ukraine, which could complicate attempts by President Joe Biden's administration to maintain and reach a follow-on agreement.
"Russia’s refusal to facilitate inspection activities prevents the United States from exercising important rights under the treaty and threatens the viability of U.S.-Russian nuclear arms control," a State Department spokesperson said in emailed comments.
Russian ambassador to the United States Anatoly Antonov was quoted by the Interfax news agency as saying that "arms control cannot be isolated from geopolitical realities" and Russia saw it as inappropriate to invite the U.S. military to its strategic facilities at the moment.
Antonov said Russia would nevertheless stick to other New START terms and limitations.
Leaders of national security committees in the U.S. Senate, which must approve treaties, said Moscow's failure to comply would affect future arms pacts.
"But to be very clear, compliance with New START treaty obligations will be critical to Senate consideration of any future strategic arms control treaty with Moscow," Democratic Senators Bob Menendez, Jack Reed and Mark Warner said in a statement.
Menendez chairs the Senate Foreign Relations Committee, Reed the Senate Armed Services panel and Warner the Senate Intelligence Committee.
Moscow in August suspended cooperation with inspections under the treaty, blaming travel restrictions imposed by Washington and its allies after Russian forces invaded neighbor Ukraine in February last year, but said it was still committed to complying with the provisions of the treaty.
The State Department spokesperson added that Russia had a "clear path" for returning to compliance by allowing inspection activities, and that Washington remains ready to work with Russia to fully implement the treaty.
"The New START Treaty remains in the national security interests of the United States," the spokesperson said.
Talks between Moscow and Washington on resuming inspections under New START were due to take place in November in Egypt, but Russia postponed them and neither side has set a new date.
On Monday, Russia told the United States that the treaty could expire in 2026 without a replacement because it said Washington was trying to inflict "strategic defeat" on Moscow in Ukraine.
Asked if Moscow could envisage there being no nuclear arms control treaty after 2026, Deputy Foreign Minister Sergei Ryabkov told the RIA state new agency: "This is quite a possible scenario."
The United States has supplied more than $27 billion in security assistance to Ukraine since the invasion, including more than 1,600 Stinger anti-aircraft rocket systems, 8,500 Javelin anti-tank missile systems and 1 million 155mm artillery rounds.