President Donald Trump’s call for the U.S. to resume nuclear testing after a more than 30-year pause has caught Russia’s attention, with the Kremlin warning on Thursday that it would “act accordingly” if a Cold War-era moratorium on nuclear weapons’ testing was broken.

Ahead of his high-profile talks with China’s President Xi Jinping in Asia on Thursday, Trump said he had instructed the Pentagon — rebranded as the “Department of War” — to resume nuclear testing.

“The United States has more Nuclear Weapons than any other country ... Russia is second, and China is a distant third, but will be even within 5 years. Because of other countries testing programs, I have instructed the Department of War to start testing our Nuclear Weapons on an equal basis. That process will begin immediately,” Trump said in a post on his Truth Social platform.

Earlier on Thursday, Kremlin Spokesperson Dmitry Peskov was asked by reporters for his reaction to Trump’s comments on resuming nuclear tests after a moratorium was introduced in 1992 following the end of the Cold War and fall of the Soviet Union.

“Trump mentioned in his statement that other countries were allegedly testing nuclear weapons. Until now, we were not aware that anyone was testing anything,” Peskov told journalists, in comments translated by NBC News.