The former supreme allied commander of NATO warned that President Donald Trump was risking millions of lives by casually threatening nuclear war on social media.

The president posted another provocative tweet Monday about North Korea as MSNBC’s “Morning Joe” broadcast, and co-host Mika Brzezinski said she was almost too terrified to read it on air.

Our country has been unsuccessfully dealing with North Korea for 25 years, giving billions of dollars & getting nothing. Policy didn't work! — Donald J. Trump (@realDonaldTrump) October 9, 2017

BBC host Katty Kay asked retired Adm. James Stavridis, the former commander of NATO forces and current dean of of the Fletcher School of Law and Diplomacy at Tufts University, whether he was aware of any behind-the-scenes military planning that would explain the president’s threats.

“I don’t see military operations beginning to unfold in a way that would lead me to believe we are setting the table for an actual full-blown military strike,” Stavridis said.

“The thing to watch are the aircraft carriers,” Stavridis continued. “You’ll read reports that an aircraft carrier deployed this morning, and it did. USS Roosevelt, nicknamed ‘The Big Stick,’ Roosevelt deployed (Monday) on schedule — long-planned, a year planned. When you see two or three carriers moving toward the Korean Peninsula, that’s setting the table, that’s getting ready for the strike zone. I’m not seeing that, but these kind of tweets do more than inch us. We are starting to really sleepwalk toward a conflict on the Korean Peninsula. A million people are going to die, and we can still avoid that if we can hold ourselves back from this kind of impetuous behavior.”