U.S. Air Force B-1B bombers and F-15 jets, flying in international waters, carried out a show of force Saturday flying off the coast of North Korea, reaching the farthest point north of the Demilitarized Zone which separates North and South Korea that any U.S. fighter or bomber aircraft has flown in the 21st century.

Pentagon spokesperson Dana White released a statement saying the operation was a display of  “the seriousness with which we take (North Korea’s) reckless behavior.”

“This mission is a demonstration of U.S. resolve and a clear message that the President has many military options to defeat any threat,” the statement read. “North Korea’s weapons program is a grave threat to the Asia-Pacific region and the entire international community. We are prepared to use the full range of military capabilities to defend the U.S. homeland and our allies.”

In a speech at the UN on Saturday, North Korean Foreign Minister Ri Yong-ho called U.S. President Donald Trump “a mentally deranged person full of megalomania” who is holding “the nuclear button.”  He added that “insults” by the U.S. president were an “irreversible mistake making it inevitable” that North Korean rockets would hit the US mainland.

On Tuesday, President Trump addressed the UN General Assembly for the first time and referred to Kim Jong Un, North Korea’s supreme leader, as a “rocket man on a suicide mission”.