TOKYO (AP) — The highest-ranking U.S. military officer on Friday encouraged Japan's commitment to doubling its defense spending over the next five years, calling Tokyo's controversial push for a stronger military crucial to confront rising threats from North Korea and China.

Gen. Mark Milley, the chairman of the Joint Chiefs of Staff, mentioned Japan's need for improvements in cruise missile defense, early warning missile systems and air capabilities, all of which would help the United States as it looks to counter North Korea's push for a nuclear missile program capable of pinpoint-targeting the U.S. mainland and China's increasing aggression against Taiwan, the democratic island that Beijing claims as its own.

China has "invested enormously in their military" and aspires to be "the regional hegemon in all of Asia, really probably in the next 10 to 15 years," Milley said.

That "could become very unstable; it could become very dangerous, and I think having a powerful Japan, a militarily capable Japan that has a close alliance with the United States and other countries, will go a long way to deterring war," Milley said.

Milley's comments to reporters at the U.S. ambassador's residence in downtown Tokyo provide an explicit U.S. military analysis of an increasingly unstable security situation in northeast Asia. With more than 80,000 U.S. troops in Japan and South Korea, and rising military moves by North Korea and China, the possibility of war in the region has become a growing worry. Washington wants its allies, particularly in Tokyo and Seoul, to do more.

Japan, meanwhile, has long wrestled with the need for a strong military amid domestic and regional wariness about anything seen as overly aggressive. Japanese soldiers overran much of Asia in the years leading up to World War II, and the nation is still viewed with anger by many in surrounding nations because of a perception that it hasn't been fully repentant.

Milley also addressed the most recent missile test-launch by North Korea, a solid-fuel ICBM that he said "clearly demonstrates an intent to develop a capability to strike the continental United States." While not providing specifics about the North's missile program, he said: "It has our attention."

Japan's budget for the coming fiscal year provides a record 6.8 trillion yen ($50 billion) in defense spending, up 20% from a year earlier. That includes 211.3 billion yen ($1.55 billion) for deployment of U.S.-made long-range Tomahawk cruise missiles that can be launched from warships and can hit targets up to 1,600 kilometers (1,000 miles) away.

The hefty defense budget is the first installment of a five-year, 43-trillion-yen ($315-billion) military spending plan as part of Japan's new National Security Strategy, which was announced in December.

The new spending target meets NATO standards and will eventually push Japan's annual defense budget to about 10 trillion yen ($73 billion), the world's third biggest after the United States and China.

"I have no doubt that the Japanese military could rapidly expand in scale, size, scope and skill very, very fast," Milley said.

Milley also spoke of the need to speed up U.S. military assistance to Taiwan, mentioning the island's need for better air defense, mines and air-to-air and shore-to-ship capabilities.

"What we're opposed to is any ... use of military to compel some sort of unification," Milley said. "Taiwan should have the capability to defend itself" as a way to deter any aggression by China.

"The speed at which we the United States or other countries assist Taiwan in improving their defensive capabilities, I think that probably needs to be accelerated in the years to come," Milley said.