U.S. Defense Secretary Jim Mattis stressed diplomacy as the way to deal with the North Korean crisis during talks with his South Korean counterpart in Hawaii on Friday, a day after Seoul's top diplomat said a military solution would be unacceptable.

"Diplomacy should impose reason on Kim's reckless rhetoric and dangerous provocations," Mattis said, referring to North Korean leader Kim Jong Un.

He added that the response to the threat remains "diplomacy-led, backed up with military options available to ensure that our diplomats are understood to be speaking from a position of strength."