MOSCOW (AP) — Russia-U.S. relations are in a state of “unprecedented crisis” without any sign of improvement, a senior Russian diplomat said Thursday.

Deputy Foreign Minister Sergei Ryabkov argued that the White House's emphasis on increasing weapons supplies to Ukraine to ensure Russia's defeat leaves no room for diplomacy.

“I don't see any prospect for a productive political and diplomatic process,” Ryabkov said at a briefing. “We have a very deep and unprecedented crisis in Russia-U.S. relations. The Biden administration has driven them into a deadlock.”

Ryabkov warned that the U.S. and its allies must carefully assess the risks stemming from supplying increasingly powerful Western weapons to Ukraine.

“The Americans need to thoroughly and deeply weigh the risks linked to their unabashedly cavalier course,” he said.

Ryabkov noted that Moscow doesn't trust Western statements about self-imposed restrictions on a range of weapons supplied to Ukraine in order to avoid escalation, adding that such assurances in the past have served as cover for a steady expansion of the assortment of arms deliveries.

“We don't see any sign of reason in any of the NATO and EU members' capitals,” Ryabkov said. “What they are doing isn’t going to strengthen their security.”

He rejected the U.S. argument that Russia’s refusal to allow the resumption of inspections of its nuclear facilities represents a breach of the New START treaty, the last remaining nuclear arms control pact between the two countries.

The New START treaty, signed in 2010 by President Barack Obama and Russian President Dmitry Medvedev, limits each country to no more than 1,550 deployed nuclear warheads and 700 deployed missiles and bombers. The agreement envisages sweeping on-site inspections to verify compliance.

Just days before the treaty was due to expire in February 2021, Russia and the United States agreed to extend it for another five years.

Russia and the U.S. have suspended mutual inspections under New START since the start of the COVID-19 pandemic, but Moscow last fall refused to allow their resumption, raising uncertainty about the pact’s future.

The U.S. State Department last week said that Russia's refusal to allow the inspections “prevents the United States from exercising important rights under the treaty and threatens the viability of U.S.-Russian nuclear arms control.” It noted that nothing prevents Russian inspectors from conducting inspections of the U.S. facilities.

Ryabkov on Thursday insisted that Russia has continued to comply with the treaty and exchange information in accordance with it. “We adhere to the treaty and observe its provisions,” he said.

At the same time, he reaffirmed Moscow’s view that resuming inspections wasn’t possible in the current environment.

Ryabkov, who met recently with the new U.S. ambassador to Moscow, Lynne Tracy, also said that the Russian Foreign Ministry has lodged a formal complaint to the U.S. Embassy, charging that its use of social networks represented interference in Russia's domestic affairs.