U.S. President Donald Trump said Friday he was sending two nuclear submarines to “the appropriate regions” after a senior Russian official posted online about Russia’s nuclear capabilities and a “step towards war” with the U.S.

Trump’s order sharply escalated a social media battle with former Russian president Dmitry Medvedev, who currently serves as the deputy chairman of the Russian Security Council and is one of the most outspoken critics of the U.S. and Ukraine’s western allies.

“I have ordered two nuclear submarines to be positioned in the appropriate regions, just in case these foolish and inappropriate statements are more than just that,” Trump wrote on his Truth Social website.

“Words are very important, and can often lead to unintended consequences, I hope this will not be one of those instances.”

Trump and Medvedev have been trading barbs all week after Trump on Monday said Russia had “۱۰ days from today” to agree to a ceasefire in Ukraine or be hit with tariffs.

That deadline was shortened from a previous timeline of 50 days.

Medvedev posted on X that same day that Trump was playing “a game of ultimatums” and warned “each new ultimatum is a step towards war.”

“Not between Russia and Ukraine, but with his own country,” Medvedev added.

Trump then posted on Truth Social early Thursday that Medvedev should “watch his words” and was “entering very dangerous territory!”