Japan's foreign minister, Fumio Kishida, also demanded a resolution to a dispute concerning Japanese citizens abducted decades ago by North Korean officials.
"The U.S.-Japan alliance have never really been stronger than it is today, " Mr. Kerry said at a news conference with his Japanese counterpart, Fumio Kishida.
On Sunday, Mr Kerry is meeting his Japanese counterpart Fumio Kishida and Prime Minister Shinzo Abe in Tokyo, where he is expected to reassure Japan of America's continued support during the crisis.