Former Russian President Dmitry Medvedev hit back at the U.S. on Wednesday, warning that his country reserved the right to use its nuclear arsenal to defend itself after a speech in Poland by President Biden following his surprise visit to Ukraine.

“After all, it is obvious to all reasonable forces that if the United States wants the defeat of Russia, then we are on the verge of a world conflict,” Medvedev, who currently serves as the deputy chairman of Russia’s Security Council, said in a post on the messaging platform Telegram. “If the United States wants to defeat Russia, then we have the right to defend ourselves with any weapon, including nuclear.”

The message from Medvedev — who was president from 2008 to 2018 and the country’s prime minister until 2020 — about nuclear weapons comes after Russian President Vladimir Putin said earlier this week that he intended to pull Russia from the New START arms treaty, an agreement between Russia and the U.S. to limit their ability to produce and launch nuclear weapons.

After Biden’s surprise visit to Ukraine on Monday, he delivered a speech in Poland in which he noted that the “United States and the nations of Europe do not seek to control or destroy Russia.”

“The West was not plotting to attack Russia, as Putin said today,” Biden said. “And millions of Russian citizens who only want to live in peace with their neighbors are not the enemy.”

He went on to lay the burden of ending the war on Putin.

“If Russia stopped invading Ukraine, it would end the war,” Biden said. “If Ukraine stopped defending itself against Russia, it would be the end of Ukraine.”

Medvedev turned the claim upside down, arguing it was actually the U.S. who was prolonging the war.

“If the US stops supplying weapons to the Kyiv regime, the war will end,” he said.