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,

Russia urged caution after Trump claimed he redeployed nuclear subs in response to provocative remarks by a senior Russian official.

President Donald Trump said he's ordered two nuclear submarines to move in the "appropriate regions" in response to recent comments from Russia's Dmitry Medvedev.