Secretary of State Rex Tillerson arrives in Asia today on his first visit to the region as America’s chief diplomat, including stops in the key capitals of Japan, South Korea and China.

With some of the world’s biggest economies and most powerful militaries, northeast Asia stacks up as one of the most important parts of the world for American interests.

It’s also a bit of a powder keg these days.

North Korea: While Pyongyang isn’t one of Tillerson’s scheduled stops, it will unquestionably dominate his talks with his Japanese, South Korean and Chinese counterparts.

With its nuclear and ballistic missile provocations, no one is very happy with North Korea right now. Indeed, it’s possible that Pyongyang will go “ballistic” — or worse — during Tillerson’s time in Asia.

Stop No. 1 — Japan: Tokyo is one of Washington, D.C.’s key allies in Asia — even globally. Japanese leaders, of course, are going to want to talk about the growing North Korean threat, but they will also want to discuss China.

The rivalry between Tokyo and Beijing is long-standing and increasingly intense, highlighted by a territorial dispute in the East China Sea over the Senkaku/Diaoyu Islands.

Japan is none too comfortable with China’s military build-up nor its island-building campaign in the South China Sea, either. While some distance from Tokyo, lots of Japanese commerce and — equally important — much- needed energy imports move through that strategic sea.

With news that Japan is reportedly sending its largest warship, a helicopter carrier, to the South China Sea on an historic months-long deployment, Tokyo will want to know Team Trump’s plans for dealing with Beijing’s boldness.

Stop No. 2 — South Korea: You’d think the only thing to talk about in Seoul these days would be naughty North Korea and its nefarious nuclear and ballistic missile programs.

While that’s generally true, our South Korean ally is also struggling with a big domestic political problem: President Park Geun-hye’s impeachment.

Last week, South Korea’s Constitutional Court affirmed Park’s December impeachment on corruption charges; she has left office. Elections must be held within 60 days.

New polls for president may or may not be good news for Washington-Seoul relations; it depends on who replaces Park in South Korea’s (presidential) Blue House.

Stop No. 3 — China: With the national power it’s amassing, Beijing’s status as competitor, challenger, enemy, “frenemy” — take your pick — of the United States makes this whistle-stop arguably Tillerson’s toughest.

Though President Trump has reportedly invited President Xi Jinping to Mar-a-Lago for a visit soon, ties between Washington and Beijing are troubled and tense.

The bilateral trade imbalance, cyberspying, South China Sea challenges, ties with Taiwan, China’s increasingly muscle-bound military, Beijing’s relations with Pyongyang and so on, will make for some difficult discussions.

For its part, Beijing will be gauging how much push-back it will get on its assertive agenda in Asia from Washington’s new crew.

Secretary Tillerson’s jaunt to Asia provides an appropriate bookend to Secretary of Defense James Mattis’ earlier visit to a region fraught with a difficult history, enduring competition and “arms racing.”

No question: Getting Asia right is critical to getting America’s foreign policy right.