The Kremlin on Monday urged caution about U.S. President Donald Trump's remarks on nuclear submarine deployment against Russia.

Trump on Friday said on Truth Social that he had ordered the deployment of two nuclear submarines "in the appropriate regions" following his spat with Dmitry Medvedev, former Russian president and deputy chair of Russia's Security Council.

Trump said Sunday that the two nuclear submarines have arrived "where they have to be," two days after he ordered their deployment.

"We are very careful about any statements related to nuclear issues ... And, of course, we believe that everyone should be very, very careful with nuclear rhetoric," said Kremlin Spokesman Dmitry Peskov.

Meanwhile, Peskov said the Kremlin does not rule out the possibility of a meeting between Russian President Vladimir Putin and Trump's special envoy Steve Witkoff this week, adding that Moscow considers contacts with the envoy "important, meaningful and very useful."

Earlier, Trump said Witkoff could go to Russia this week. On April 25, Putin and Witkoff discussed the possibility of direct Russia-Ukraine talks during the envoy's last visit to Moscow.

On July 28, Trump cut short the deadline for Moscow to end the conflict with Ukraine to "10 or 12 days" from the initial 50-day timeline, citing disappointment with "Moscow's lack of willingness to compromise." Later that day, Medvedev said Trump is playing an "ultimatum game with Russia," calling his threat "a step towards war ... with his own country."