President Trump winged his way to Asia on Saturday, with Japan the first stop on a region-wide tour devoted to arguments about trade and worries about North Korea's nuclear weapons.

Trump boarded Air Force One early in the day in Hawaii, where he made a mid-way stop to tour the Pearl Harbor battle memorial and received a briefing from military leaders at the U.S. Pacific Command.

"Thank you to our GREAT Military/Veterans and @PacificCommand," Trump tweeted. "Remember #PearlHarbor. Remember the @USSArizona! A day I’ll never forget."

Trump is scheduled to arrive in Tokyo on Sunday morning, local time.

Japanese Prime Minister Shinzo Abe is expected to welcome Trump with pomp and ceremony, plus a round of golf.

Behind the scenes, however, Japanese leaders still wonder about Trump's harsh criticism of U.S. trade deals with other countries, and worry about getting caught in the middle if tensions with North Korea lead to military conflict, maybe even one with nuclear weapons.

"There is an underlying element of anxiety in Japan," said Michael J. Green, senior vice president for Asia and Japan chair with the Washington-based Center For Strategic & International Studies.

After a couple of days in Japan, Trump plans to emphasize trade and North Korea nukes during visits to Seoul and Beijing. He wraps up the trip by attending economic conferences in Vietnam and the Philippines.

Trump is using the trip in part to push Asian countries to pressure North Korea into giving up its nuclear weapons. Most of that effort is focused on China, which is North Korea's neighbor and leading economic patron.

While Trump plans to focus on North Korea, he and aides will be watching to see whether regime leader Kim Jong Un tries to grab the world's attention with some kind of nuclear test during the trip.

Back in February, Kim fired a missile over Japan as Abe and Trump met at the president's Mar-a-Lago estate in Palm Beach, Fla.

Abe is mirroring that visit in hosting Trump, including the golf outing. The leaders, as well as Japanese star Hideki Matsuyama, will play at Kasumigaseki Country Club, site of the golf competition when Japan hosts the 2020 Olympics.

In terms of trade, Japan is looking for the way forward after Trump began his administration by killing off the proposed Trans-Pacific Partnership, a Pacific Rim trade deal in which Japan would have been a key player. The Trump administration has talked about a bilateral trade agreement with Japan, but some Japanese officials do not know what that would entail.

Abe is in a strong domestic political situation as he welcomes Trump to Japan, having racked up wins in recent parliamentary elections.

Trump, meanwhile, faces intense political opposition at home, as well as investigations into whether his campaign team colluded with Russia as it sought to influence the 2016 presidential election, claims Trump vehemently denies.

In leaving the White House on Friday, Trump began his Asia trip by tweeting about Hillary Clinton and other matters.

Mireya Solis, senior fellow with the Center For East Asia Policies at the Brookings Institution, said some officials in Asian countries worry about presidential distractions.

"Leaders in the region are wondering how much of the attention will be on the regional issues that are so pressing," Solis said.