Former Soviet leader Mikhail Gorbachev said Wednesday he has “great concern” about the relationship between the U.S. and Russia and that newly sworn-in President Biden should work to “normalize relations” between Washington and Moscow.

“The current condition of relations between Russia and the United States is a great concern. Unfortunately, this is a hard fact,” Gorbachev said in an interview with state news agency TASS. “But this also means that something has to be done about it in order to normalize relations.”

“[Y]ou have to start somewhere; we cannot fence ourselves off from each other.”

Relations between the U.S. and Russia have deteriorated in recent years amid disputes over arms treaties and after Moscow was accused of meddling in 2016 presidential election.

Biden repeatedly railed against President Vladimir Putin on the campaign trail, casting the Russian leader as a strongman who interfered in the U.S.’s democratic process and works against its interests in Europe.

“I believe Russia is an opponent. I really do,” Biden said at a town hall last year. “And look, Putin’s overwhelming objective is to break up NATO, to fundamentally alter the circumstance in Europe so he doesn’t have to face an entire NATO contingent.”

However, Gorbachev, who signed the Strategic Arms Reduction Treaty, or START I, with President George H.W. Bush in 1991, pointed to that landmark agreement as evidence that even two bitter rivals can come together when the need arises.

“I recall the mid-1980s,” Gorbachev told TASS. “People were saying that nothing would work out relations with the United States. But we resumed the dialogue, met at the highest level — after a six-year break — and adopted a joint statement.”

“We agreed to intensify contacts at all levels and our exchanges and cooperation.”

The former Soviet leader said it is unclear if tensions will rise even further during a Biden administration but maintained it was paramount that Biden and Putin come together to agree on “certain rules of the game, and then see to it they are followed.”

“If they are not respected, we should talk frankly about it and discuss what is wrong, what is the problem,” he said. “In a word, it is the diplomats’ realm of responsibility.