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CNN  — 

White House national security adviser Robert O’Brien on Friday rejected Russian President Vladimir Putin’s proposal to extend New START, a key arms control treaty, for one year without any additional agreements, calling the offer a “non-starter.”

“The United States proposed an extension of New START for one year, in exchange for Russia and the United States capping all nuclear warheads during that period. This would have been a win for both sides, and we believed the Russians were willing to accept this proposal when I met with my counterpart in Geneva,” O’Brien said in a statement released on the White House’s National Security Council Twitter feed.

“President Putin’s response today to extend New START without freezing nuclear warheads is a non-starter,” he said.

He threatened a “costly” arms race if Russia does not come back to the table with a better proposal: “The United States is serious about arms control that will keep the entire world safe. We hope that Russia will reevaluate its position before a costly arms race ensues.”

The top US negotiator, Marshall Billingslea, suggested in a tweet later Friday that talks between the two countries were over.

“The United States made every effort. It is disappointing that the Russian Federation backtracked on an agreement covering all nuclear warheads for the first time. This would have been an historic deal, good for the U.S., Russia, and the world,” he wrote.

Trump has been urging his national security team to secure a nuclear deal with Russia before the November election, sources familiar with the efforts tell CNN. He had initially wanted to bring China into the deal, but China has repeatedly rejected partaking in any discussions. Russia has now also rejected a number of US proposals to get it to agree to a series of additional commitments in order to renew New START.

Russia’s latest proposal, met by a swift US rejection, means the chances are low for striking a deal before the US presidential election.

It was in a meeting with his advisers Friday that Putin proposed to extend the nuclear arms reduction treaty for a year without preconditions.

“In the past years, the treaty worked properly, fulfilled its fundamental role of limiting, curbing the arms race,” Putin said. “I have a proposal: to extend the existing Treaty without any conditions for at least a year in order to be able to conduct meaningful negotiations on all parameters … so as not to leave our countries and all states of the world without such a fundamental document.”

O’Brien’s rejection of Putin’s offer comes days after Billingslea said the US and Russia had achieved “agreement in principle, at the highest levels of our two governments, to extend the treaty.”

That statement was flatly rejected by Russia, which said that no such agreement had been established.

Billingslea had previously indicated in an interview with a Russian newspaper that the Trump administration was looking to reach an agreement before the presidential election. Russian Deputy Foreign Minister Sergey Rybakov rejected the idea, saying the US would not get an agreement on strategic arms control from the Kremlin in the run-up to the election.

The landmark New Strategic Arms Reduction Treaty, set to expire on February 5, is the last treaty between the US and Russia placing limits on the growth of the world’s two largest nuclear arsenals, since the US formally withdrew from the Intermediate Range Nuclear Forces treaty in August 2019.

The US side has tried to urge Russia to accept the US proposal to extend the treaty, and agree to additional US terms. Last month Billingslea threatened Russia that the Trump administration could increase the cost of extending New START – by “including a lot of the other bad behavior that the Russians are engaged in around the world” in the nuclear negotiations – if Moscow does not commit to meeting US demands before the American presidential election.

Trump administration officials have asked the US military how long it would take to load existing nuclear weapons onto bombers and submarines if the treaty is not extended next year, according to a source familiar with the discussions. This order demonstrates that the administration has begun preparing for the possibility that the arms treaty falls apart.

During a discussion with the Aspen Security Forum on Friday, O’Brien said, “We’ll have to wait and see, and see how that plays out,” regarding discussions with the Russians over extending New START. “They certainly are tough negotiators. It’s a dangerous situation.”

This story has been updated with comments from US negotiator Marshall Billingslea.

CNN’s Mary Ilyushina contributed to this report from Moscow.