"Trump’s Make America Great Again slogan, if it means nuclear supremacy, will plunge the world back into the 50-60s when the nuclear arms race was at its worst," the Russian lawmaker wrote on Facebook.
Trump said in a recent interview the New START treaty was "just another bad deal" and argued the United States had fallen behind in terms of nuclear capabilities. He did not specify whether he was going to abolish the deal with Russia or let it expire.
Kosachev, who chairs Russia's upper-house Foreign Affairs Committee, said the Trump administration needed to make up its mind now because the New START did not have an automatic renewal clause.
"Are we about to enter a new era? I think we need a quick answer to this question, and the best response would be a high-level agreement on new US-Russian consultations," the lawmaker concluded.
The pact was signed by the United States and Russia in 2010. The nations agreed to cut the number of deployed nuclear warheads to 1,550 and the number of deployed missiles and bombers to 700.