US President Donald Trump says he has ordered two nuclear submarines to "be positioned in the appropriate regions" in response to "highly provocative" comments by former Russian President Dmitry Medvedev.
Trump says he acted just in case these foolish and inflammatory statements are more than just that.
He says words are very important, can often lead to unintended consequences, and he hopes this will not be one of those instances.
He did not say where the two submarines were being deployed, in keeping with US military protocol.
Medvedev has recently threatened the US in response to Trump's ultimatums to Moscow to agree to a ceasefire in Ukraine, or face tough sanctions.
Russia and the US possess the most nuclear arms in the world, and both countries have a fleet of nuclear submarines.
