NATO Secretary-General Mark Rutte on Tuesday said Japan's role is increasingly important as the alliance monitors China's "rapid" military expansion.
"Tokyo is of particular importance," said Rutte, warning that Beijing is "building up its armed forces, including its navy, at a rapid pace."
"We cannot be naive and we really have to work together to assess what is happening," he said during a visit to the Yokosuka Naval Base on Honshu Island.
Rutte told reporters the US had urged NATO to increase its engagement with the Indo-Pacific Four-Japan, Australia, New Zealand and South Korea-not through collective defense under Article 5, but through cooperation in defense, industrial capacity, and innovation.
He said the alliance is concerned about recent Chinese military drills near Taiwan.
His visit follows US Defense Secretary Pete Hegseth's trip to Japan last month, during which he reaffirmed that the US-Japanese alliance remains the "cornerstone of freedom, prosperity, security, and peace in the Indo-Pacific."
Last year, reports emerged that NATO was considering opening its first office in Asia, possibly in Tokyo. In January, Japan launched its own NATO mission in Brussels.
Beijing and North Korea have warned against NATO's presence in the region, accusing it of trying to form an "Asian NATO."
Japan is the only member of the Group of Seven that is not part of NATO.
Rutte is in Tokyo on a two-day visit and is expected to meet Prime Minister Shigeru Ishiba and other officials.
