WASHINGTON (AP) — In a warning to Russia, President Donald Trump said Friday he’s ordering the repositioning of two U.S. nuclear submarines “based on the highly provocative statements” of the country’s former president, Dmitry Medvedev, who has raised the prospect of war online.

The Kremlin has tried to calm tensions in a feud between Trump and Medvedev that spiraled into nuclear threats.

President Trump is rattling the U.S.’s formidable nuclear saber amid his growing frustration with Russian President Vladimir Putin’s refusal to halt the war in Ukraine, just days ahead of Trump’s deadline for a ceasefire.