The top commander of U.S. forces in the Asia-Pacific region reassured Tokyo on Thursday that Washington remains committed to the defense of Japan, amid concern over a weakening commitment given the cancellation of an annual military exercise.

"The steadfast alliance between Japan and the United States is an enduring force for peace and stability in the Pacific region...we remain committed to our mutual alliance, the defense of Japan," Adm. Philip Davidson, the head of the U.S. Indo-Pacific Command, told Japanese Prime Minister Shinzo Abe at their meeting in Tokyo.

Tokyo has been uneasy since the United States and South Korea announced this week the cancellation of the Ulchi Freedom Guardian exercise scheduled for August, fearing such a move could weaken the deterrence effect in the region provided by the U.S. military.

The announcement followed the historic June 12 summit between U.S. President Donald Trump and North Korean leader Kim Jong Un, who committed "to work toward complete denuclearization of the Korean Peninsula."

Japanese Defense Minister Itsunori Onodera, who also met Davidson earlier in the day, said North Korea has yet to take "any concrete and visible actions" toward denuclearization following the summit, emphasizing the importance of Japan-U.S. cooperation in closely monitoring its moves.

Davidson, who assumed the commander's post in late May, told Onodera that the United States is "firmly committed to the complete, verifiable, and irreversible denuclearization of the Korean Peninsula."

(Japan Defense Minister Itsunori Onodera, right, and Adm. Philip Davidson in Tokyo)

"We affirmed that sanctions (on North Korea's nuclear and weapons development programs) will remain unless CVID is properly achieved," Onodera told reporters after the meeting.

The Japanese defense chief also said he agreed with the U.S. commander that the halt of the U.S.-South Korea military exercise was intended to "support" diplomatic efforts to make North Korea give up its nuclear weapons and, if North Korea fails to take action, the drill would take place.

"The halt means that we are assessing North Korea's moves," Onodera said.

For Japan and South Korea, military exercises conducted with the United States have been used as a tool to pressure North Korea to give up on its nuclear and missile ambitions. North Korea has denounced the Ulchi Freedom Guardian -- an annual U.S.-South Korea command and control exercise that began in 1976 -- as a rehearsal for invasion.

Trump surprised U.S. allies when he said at a press conference after the summit with Kim, "We will be stopping the war games (with Seoul), which will save us a tremendous amount of money, unless and until we see the future negotiation is not going along like it should."