U.S. Vice President Kamala Harris, second from left, visits the demilitarized zone (DMZ) separating the two Koreas in Panmunjeom, Thursday. Yonhap

U.S. Vice President Kamala Harris said Thursday that Washington will do "everything in our power" to ensure its security commitment to South Korea, amid growing North Korean nuclear and missile threats.

Harris made the remarks after a tour of the Demilitarized Zone (DMZ) separating the two Koreas. She arrived here from Japan earlier in the day, following two rounds of North Korean missile launches this week.

"I cannot state enough that the commitment of the U.S. 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 the words suggest," she told reporters.

Harris reaffirmed America's extended deterrence to its Asian ally, which she said is supported by the "full range of U.S. military capabilities."