US President Donald Trump said on Friday he has ordered two nuclear submarines "to be positioned in the appropriate regions" in response to remarks from Deputy Chairman of the Russian Security Council Dmitry Medvedev.

Trump did not specify in a Truth Social post the deployment locations, which are kept secret by the U.S. military. Not all the U.S. nuclear-powered submarines are equipped with nuclear weapons.

Medvedev on Monday accused Trump of playing the ultimatum game with Russia, warning "each new ultimatum is a threat and a step towards war. Not between Russia and Ukraine, but with his own country," he wrote on social media platform X.

Trump said Tuesday that his 10-day "deadline" for Moscow to end the conflict with Ukraine is in effect. He told reporters on his flight back to Washington following his visit to Scotland. Otherwise, "We're going to put on tariffs and stuff."