Secretary of State Rex Tillerson opened up his first official trip to Asia announcing that the US would consider “all options” to deal with the growing nuclear threat from North Korea.

He even refused to rule out having Japan and South Korea develop their own nuclear weapons in an interview with Fox News.

In March 2016, before North Korea’s nuclear testing had quite reached the fever pitch it’s at today, Trump proposed allowing South Korea and Japan to develop their own nukes to protect themselves.

The proposal was widely panned by nuclear-proliferation experts.

But Tillerson now stresses that all options are on the table for dealing with North Korea, and that could include more countries building nuclear weapons.

Daryl Kimball, executive director of the Arms Control Association, told Business Insider the idea that North Korea’s nuclear posturing could be answered with further nuclearization of the region was “foolish, simplistic, and naive,” and “deeply, deeply troubling.”

“If all options are on the table, that should mean that diplomacy and talks with North Korea are on the table,” said Kimball, who acknowledged that “Tillerson is right that, up to now, US administrations have not succeeded in denuclearizing North Korea.”