Russia is uninterested in broadening the New START treaty to cover new weapons, the country’s ambassador to the United States said Monday. That’s a blow to the last remaining major arms control agreement between the two original nuclear powers.

The New Strategic Arms Reduction Treaty, or START, which expires in 2021, governs specific nuclear weapons belonging to the United States and Russia — essentially, the ones that existed when the agreement went into effect eight years ago. But Russia has been developing new nuclear weapons and delivery systems such as the Poseidon nuclear-armed submarine drone, the Burevestnik nuclear-powered cruise missile, and new hypersonic missiles. “I want, ideally, all nuclear weapons to be part of New START, not just the ones that are in the Treaty now,” Gen. John Hyten, the head of U.S. Strategic Command, told the Senate Armed Services Committee in March.

Some have argued that renewing New START without extending the types of weapons it covers would be “a gift” to the Kremlin.

Anatoly Antonov, Russia’s ambassador to the United States, said that was a nonstarter. “We have to stick with the provisions of the Treaty,” Antonov said at the Carnegie Endowment's nuclear policy conference.

The ambassador declared that any discussion of weapons not currently in New START should be part of a separate discussion about other issues. He rattled off a list of U.S. actions, programs, research activity, etc., that Russia takes exception to, which would conceivably by part of the new side discussion. They included U.S. missile defense in Europe; conventional armed forces in Europe; and cyber security. “What about the possibility to deploy weapons of any type in outer space?” he asked, referring to current Pentagon research into the feasibility of what’s called “space-based intercept” as well as current research into outfitting the F-35 Joint Strike Fighter with new weapons to take out missiles on the launch pad.

“We are very concerned with what is going in the United States in terms of strategic defensive arms,” he said, referring to the space-based intercept and F-35 concepts.

The message was clear: if you want to talk about our newest nuclear weapons, we can have a big discussion about all sorts of things; but Russia is not interested in amending the New START Treaty to include her new nukes.

Antonov then went on to claim that the evidence showing that Russia is in violation of the INF was a “fairy tale” and also suggested that his country has no doctrine allowing for the first-use of nuclear weapons — despite the fact that it does. Here’s the 2014 version of the Military Doctrine: “Russia reserves the right to use nuclear weapons in response to a use of nuclear or other weapons of mass destruction against her and (or) her allies, and in a case of an aggression against her with conventional weapons that would put in danger the very existence of the state.”

Antonov’s counterpart on the panel, James Miller, who served as defense undersecretary for policy until 2014, sounded similarly down on the prospect of renewal. “There is no certainty at all that this Administration would agree to an extension” even though, Miller said, doing so was “strongly in the interests of the United States.”