"So, the United States shares a very important relationship, which is an alliance with the Republic of North Korea. And it is an alliance that is strong and enduring," Harris said Thursday at the start of her speech in the Demilitarized Zone, or DMZ, where she visited at the end of a tour to Japan and South Korea.

Apparently not noticing her misstep, Harris went on to deliver the rest of the speech, which provided a robust reaffirmation of Washington's alliance with Seoul in the face of nuclear-armed North Korea.

"I cannot state enough that the commitment of the United States to the defense of the Republic of Korea is ironclad and that we will do everything in our power to ensure that it has meaning in every way that the words suggest," she said.

"This includes our extended deterrence commitment, which is supported by the full range of US military capabilities."

North Korea test fired two ballistic missiles Thursday, Seoul's military said, Pyongyang's third such launch in less than a week and just hours after Harris left South Korea.