The war of words just escalated to something far more ominous...

On Tuesday, former Russian President Dmitry Medvedev issued the Kremlin's response to President Trump's Monday announcement from Scotland that he's reducing a deadline for Russia to agree a peace settlement from 50 days to 10 or 12 days, citing 'disappointment' in Putin not ending or at least winding down the war.

Medvedev warned: "Russia isn't Israel or even Iran" and thus that "Each new ultimatum is a threat and a step towards war. Not between Russia and Ukraine, but with (Trump's) own country."

That followed comments by Medvedev that Trump 'steamrolled, humiliated' Europe with his trade deal.

Then Thursday, Trump told Medvedev to "watch his words"