Donald Trump escalated tensions with Russia by ordering two U.S. nuclear submarines to reposition themselves near Russian waters.

President Donald Trump issued a rare threat of nuclear escalation on Friday, saying he had ordered two nuclear submarines to be strategically positioned near Russia in response to what he said were aggressive remarks by Dmitry Medvedev, the country’s former president and current deputy chairman of its Security Council.

In response to threats by former Russian President Dmitry Medvedev, US President Donald Trump on Friday said he had ordered two nuclear submarines to be positioned in regions near Russia.