Former Russian President and current Deputy Chairman of Russia’s Security Council, Dmitry Medvedev, has warned former U.S. President Donald Trump of the potential for World War III after Trump referred to Russian President Vladimir Putin as “crazy” in the context of the ongoing war in Ukraine.

According to AFP, the U.S. has labeled Medvedev’s remarks as “reckless” and “unexpected.” However, despite the rising tensions, diplomatic communication between Washington and Moscow appears to be continuing.

On Wednesday, two U.S. embassy officials—Eric Jordan and Jeremy Ventuso—participated in an international security conference held in Moscow. This marked the first such diplomatic presence since the Russia-Ukraine war began.

The war of words began last week when Trump called Putin “crazy” and later wrote on Truth Social, “Putin doesn’t realize that if I weren’t around, something very bad would have happened to Russia. He is playing with fire.”

In response, Medvedev stated, “There’s only one truly terrifying thing I know—World War III. I hope Trump understands that.”

Reacting to Medvedev’s threat, Trump’s special envoy on Ukraine, Keith Kellogg, wrote on X (formerly Twitter), “Threatening World War III is inappropriate and unfortunate for a global power. President Trump is working to end the war. We are still waiting for the peace proposal Russia promised a week ago.”