Updated

U.S. Secretary of State Rex Tillerson said Thursday cooperation with allies Japan and South Korea is "critical" to addressing the threat from North Korea's nuclear and missile programs.

Tillerson was speaking as he met with Japanese Foreign Minister Fumio Kishida on his first trip to Asia as the top U.S. diplomat.

North Korea is expected to top the agenda at Tillerson's talks in Tokyo. Last week, North Korea test-fired four missiles that landed in ocean off Japan.

Tillerson will meet later Thursday with Japanese Prime Minister Shinzo Abe.

Japan and South Korea both host tens of thousands of U.S. troops. Washington has been urging the two nations to step security cooperation despite their historically strained relations. This week, the nations' three navies have conducted missile defense information-sharing drills in the region

Tillerson said that strengthening U.S. relations with Japan and trilateral cooperation among all three "is critical in particular as we address North Korea's nuclear and missile programs."

Kishida said the fact that Japan was Tillerson's first stop showed the importance Washington attaches to the relationship. He said the U.S. and Japan had an "unwavering bond."

On Friday, Tillerson travels to South Korea, where U.S. forces are engaged in annual military drills that have angered Pyongyang.

He then goes to China. Washington wants Beijing to exert more pressure on North Korea over its provocative behavior.