Russian Foreign Minister Sergei Lavrov warned there’s a “serious” risk of nuclear war over Ukraine, even as he signaled the Kremlin is willing to talk to the U.S. to try to resolve the confrontation.

“The danger is serious, real. It can’t be underestimated,” Lavrov said in a state TV interview broadcast late Monday. Invoking the Cuban missile crisis of 1962, when the U.S. and the Soviet Union came close to nuclear war, Moscow and Washington had understood the rules of conduct between the superpowers, he said, “now there are few rules left.”

Russia will continue negotiations with Ukrainian President Volodymyr Zelensky’s representatives to try to reach a peace agreement, Lavrov said. It would be “useful” to hold discussions with the U.S. too, “but we don’t observe any interest on their part regarding contacts on Ukraine or on other issues.” Both sides have said the talks are at a dead end.

Lavrov’s comment came after U.S. Defense Secretary LLoyd Austin said Monday in Kyiv that Washington wants to see Russian forces “weakened to the degree that it can’t do the kinds of things that it has done in invading Ukraine.” The U.S. announced additional military aid for Ukraine as the war enters its 62nd day with Russian and Ukrainian armies facing off in the eastern Donbas region, where Moscow has regrouped its forces after failing to take Kyiv early in the invasion.

Austin is hosting North Atlantic Treaty Organization counterparts and other partners at Ramstein Air Base in Germany on Tuesday to discuss ways of boosting weapons supplies to Ukraine. Germany will allow delivery of 50 Gepard anti-aircraft tanks to Ukraine in its first step to supply heavy weapons to counter Russia’s invasion.

Lavrov has warned previously of the risks of a nuclear confrontation over Ukraine even as he has repeatedly declared that Russia’s “principled” position is the “inadmissibility of nuclear war.” He isn’t responsible for military decision-making in Russia and hasn’t explained how he believes a nuclear conflict would begin.

Russia will continue to pursue the war aims announced by President Vladimir Putin to secure the “destruction of military infrastructure” and the “demilitarization” of Ukraine, Lavrov said in the interview.

United Nations Secretary-General Antonio Guterres is in Moscow on Tuesday for talks with Putin and Lavrov as he strives to secure a halt to the war. The UN’s top diplomat is due to travel to Kyiv to meet with Zelenskiy on Wednesday.

In his latest daily video address, Zelensky said Russia “will lose” the war and called on Ukrainians to “think every day about how to make the occupiers’ presence on our land even more unbearable.”

Meanwhile, two antennas that carried Russian radio broadcasts in Moldova’s breakaway Transnistria region were blown up early Tuesday, the second episode of violence reported in the Moscow-backed enclave that borders Ukraine in as many days.