Tesla CEO Elon Musk warned on Friday that the North Korean threat pales in comparison to the danger posed by artificial intelligence.

"If you're not concerned about AI safety, you should be. Vastly more risk than North Korea," Musk tweeted, along with the photo of a framed poster that says "In the end the machines will win." The poster appears to address gambling addiction.

If you're not concerned about AI safety, you should be. Vastly more risk than North Korea. pic.twitter.com/2z0tiid0lc — Elon Musk (@elonmusk) August 12, 2017

"Nobody likes being regulated, but everything (cars, planes, food, drugs, etc) that's a danger to the public is regulated," he added. "AI should be too." Musk has, in the past, spoken of the need for "proactive" regulation to protect people from AI

Musk's warning caps a week of soaring rhetoric between President Trump and North Korea. North Korea, which has a nuclear weapons program and has been testing intercontinental ballistic missiles, threatened a strike on the U.S. territory of Guam. Trump promised "fire and fury" should North Korean aggression continue.

Musk, a billionare whose other business ventures include SpaceX, has repeatedly warned about the dangers of AI. In July, he told America's governors that people "should be really concerned" about artificial intelligence, which "is a fundamental risk for human civilization."

Musk mentioned how most people can't fathom the threat until robots are "going down the street killing people."

"They don't know how to react because it seems so ethereal," he said, before repeating, "We should be really concerned about AI"

On Friday, before his dire warning about AI, Musk commented on a computer that won in a computer game competition against a human.

"OpenAI first ever to defeat world's best players in competitive eSports. Vastly more complex than traditional board games like chess & Go," he tweeted. Musk is co-founder and chairman of OpenAI.