A top Russian diplomat said Friday that he is not optimistic that the U.S.-Russian nuclear arms agreement will be extended because of Washington’s demands to include China in the proposal.

Foreign Minister Sergey Lavrov cautioned the Trump administration that Russia will continue to protect its security defenses, with or without the New START treaty, noting they are likely unwilling to accept Washington’s new demands.

The New Strategic Arms Reduction Treaty (START) was signed in 2010 by former President Barack Obama and then Russian President Dmitry Medvedev. The agreement, made in accordance with the 1987 Intermediate-range Nuclear Forces Treaty, limited the number of deployed nuclear warheads to no more than 1,550 along with 700 missiles and bombers.

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Both the U.S. and Russia pulled out of the original 1987 nuclear arms agreement last year, leaving the New START treaty as the last line of defense against nuclear proliferation between the world’s leading nations in nuclear development.

If the treaty expired it would be the first time the U.S. and Russia were not united in a nuclear arms treaty since the Cold War.

“We only need the extension as much as the Americans do,” Lavrov said during a conference call with foreign policy experts Friday. “If they categorically refuse, we will not try to persuade them.”

Russia has said they would extend the treaty, which is set to expire Feb. 2021, without any additional provisions. But the Trump administration is now pushing for a new agreement that would include China.

Russia security officials are claiming this new agreement is unrealistic, and point to China’s repeated refusals to negotiate an arms deal that requires they reduce their number of nuclear arms.

The U.S. and Russia account for more than 90 percent of the world’s nuclear arms, according to Defense News.

China has said they are committed to a no first-use policy -- a nuclear deterance strategy that means China won’t strike first. However, China is working to increase its nuclear forces and has reportedly expanded its response capabilities, as reported by Defense News.

Lavrov rejected the U.S.’s calls to have Russia negotiate with China on reducing its nuclear arms arsenal, calling it “undiplomatic”. He said that they would be happy to discuss nuclear arms reductions with any country whether it’s Britain, France or China but said it needs to be that country’s decision.

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“I’m not particularly optimistic about the New START in view of the course taken by U.S. negotiators,” Lavrov said.

Lavrov said that the administration’s new stance on nuclear arms is making it more unlikely an agreement can be reached, adding “we are absolutely confident that we can guarantee our security for a long perspective, even in the absence of this treaty.”

The U.S’s new contingency comes amid increasingly strained tensions between the U.S. and China – Lavrov note that the feud could hurt the global economy.

But when asked if Russia could assist in brokering their relationship Lavrov said “If they ask us, if they show such interest, we won’t refuse to do so.”

“We’ve established contact with both parties,” Lavrov said. “We are always ready to try to help, but, of course, we won’t push our services on anyone.”

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Russia is now debating pulling out of the Open Skies Treaty, which allows for observation flights over military facilities, after Trump announced in May the U.S. may be pulling out of the 2002 agreement.

“We will make a final decision on whether to stay in it after we weigh all the consequences of the U.S. withdrawal,” Lavrov said.

The European Union has urged the U.S. to reconsider.

The Department of State could not be reached to answer whether or not the U.S. would allow the nuclear arms treaty with Russia to expire if China refuses to sign the new agreement.

The Associated Press contributed to this report.