Two days after meeting with Chinese president Xi Jinping, U.S. Secretary of Defense Jim Mattis was in Tokyo reaffirming the United States' firm commitment to the defense of Japan in any conflict against China.

Mattis told America's most powerful military ally in Asia on June 29 that "The U.S.-Japan alliance is a cornerstone of Indo-Pacific stability, and our commitment to this alliance remains ironclad." Mattis later met with Minister of Defense Itsunori Onodera and used this occasion to comment on the strength of the U.S.-Japan alliance.

Mattis said the meeting on Friday was his fifth with Onodera in just over three months. He emphasized that the frequency of their meetings "represents how strong we prioritize this relationship between our two militaries."

Mattis and Onodera together said they'd work towards the denuclearization or removal of all of North Korea's nuclear weapons. They also pledged to seek the dismantling of North Korea's short-, medium, and intermediate-range ballistic missiles (or those capable of hitting a target 1,000 km to 5,500 km away) capable of striking Tokyo. The distance from Pyongyang to Tokyo is some 1,300 km.

Military analysts said Mattis' main mission in Japan is to allay its ally's fears the U.S.' commitment defend Japan and Asia is wavering with president Donald Trump's inconsistent policies and pronouncements about North Korea. Tokyo is particularly unnerved by Trump's unilateral cancellation of a decades-old joint military exercise involving U.S. military forces with the Republic of Korea Armed Forces. It is, however, terrified Trump might soon withdraw U.S. military forces from South Korea.

"Regarding the pause of U.S.-ROK joint military exercises, this decision was taken to create space for our diplomats to negotiate strongly, and increase the prospect for a peaceful solution on the peninsula," Mattis said in apology.

"Our objective remains the complete, irreversible and verifiable dismantling of North Korea's nuclear and ballistic missile programs," said Mattis.

Mattis said the U.S. is "in the midst of very unprecedented negotiations right now with North Korea. But in this dynamic time, the longstanding alliance between Japan and the United States stands firm."