During his first visit to the Demilitarized Zone between North and South Korea, U.S. Secretary of Defense Jim Mattis said Friday that the U.S. was doing all it could to resolve its ongoing dispute with North Korean leader Kim Jong Un.

Addressing both U.S. and South Korea troops at the 38th Parallel, Mattis stressed the importance of diplomacy as the most effective way of preventing a nuclear confrontation with Pyongyang.

"We're doing everything we can to solve this diplomatically -- everything we can," Mattis told the troops after stepping out from a Black Hawk helicopter.

Tensions between the U.S. and North Korea have been escalating following weapons tests and threatening rhetoric by the Kim regime -- as well as equally ominous rhetoric from the Trump administration.

Vice President Mike Pence visited the DMZ in April.

In what looked like an attempt to defuse tensions, North Korea announced Friday that it would release a South Korean fishing vessel that allegedly crossed illegally into North Korean waters, Reuters reported.

The boat was seized Saturday and both the vessel and its crew will be released in the waters of the Demilitarized Zone.

The Associated Press contributed to this report.