President Trump touched down in Japan on Sunday morning — Saturday night in the United States — to start a tour of Asia devoted to arguments about trade, worries about North Korea's nuclear weapons, and probably a meeting with Russian President Vladimir Putin.

Saying he will likely meet with the Russian leader on the sidelines of an economic conference in Vietnam later this week, Trump told reporters aboard Air Force One, "We want Putin's help on North Korea."

Trump, who travels to Asia amid investigations into Russia interference in the 2016 presidential election, said North Korea would be "a big subject" this week, calling it "a big problem for our country and for the world, and we want to get it solved."

During a brief question-and-answer session aboard Air Force One, Trump also:

• Disputed suggestions that Chinese President Xi Jinping is coming into his meetings with Trump this week in an especially strong political position. "Excuse me, so am I," he said, citing the "highest stock market in history, lowest unemployment in 17 years, a military that’s rapidly rebuilding, ISIS is virtually defeated in the Middle East."

• Declined to combat criticism from Republican predecessors George H.W. Bush and George W. Bush. "I’ll comment after we come back. I don’t need headlines."

• Echoed his goals for the weeklong trip that will take him to Japan, South Korea and China, as well as Asian economic conferences in Vietnam and the Philippines: "Our big focus is going to be obviously on North Korea. But a very, very big focus is going to be on fair trade. And that’s very important to me."

After landing at Yokota Air Base, Trump spoke to military services members and thanked them for their work and sacrifice. Donning a bomber jacket, the president also spoke about his goals for the trip and made campaign-style remarks about the rise of the stock market and the fall in American unemployment rates.

"We always fight for what we believe in," Trump said.

Trump planned to devote a low-key opening day to lunch with Japanese Prime Minister Shinzo Abe and a round of golf with Abe and Japanese links star Hideki Matsuyama. The president and first lady Melania Trump will cap their first day in Asia at a dinner with the prime minister and spouse Akie Abe.

Melania Trump looks at pearls in Tokyo's upscale shopping district

Air Force One landed at Yokota Air Base in western Tokyo, where a group of U.S. service members awaited the arrival of the commander in chief. Shortly before landing, Trump tweeted, "Can’t wait to be with our GREAT MILITARY. See you soon!"

As often happens on presidential foreign trips, domestic politics intruded on Trump's trip to the East — in this case, the Russia investigation as well as another spat with his Republican predecessors, George H.W. Bush and George W. Bush.

The elder Bush called Trump a "blowhard," while George W. Bush said "this guy doesn't know what it means to be president," the author of a new book told CNN.

The White House struck back with a harsh statement issued while Trump winged his way to Japan.

"The American people voted to elect an outsider who is capable of implementing real, positive, and needed change — instead of a lifelong politician beholden to special interests," White House spokeswoman Sarah Sanders. "If they were interested in continuing decades of costly mistakes, another establishment politician more concerned with putting politics over people would have won.”

In addition, a pre-trip interview of Trump included questions about the Russia investigation being conduced by Special Counsel Robert Mueller.

On the syndicated television program Full Measure, Trump said he dismissed the now-indicted Paul Manafort from his campaign in 2016 because of his involvement with "certain nations," and "we don't want to have many potential conflicts." A grand jury indictment unsealed last week accused Manafort of money laundering and other charges related to his work with pro-Russian officials in Ukraine.

Trump, who has denied any involvement with Russians who sought to interfere in the 2016 election, also told the program he has no plans to dismiss Mueller.

"Well, I hope he's treating everything fairly, and if he is, I'm going to be very happy, because when you talk about innocent, I am truly not involved in any collusion with Russia," Trump said.

En route to Japan, Trump boarded Air Force One early in the day in Hawaii, where he had 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."

Before leaving Hawaii, Trump stopped for a visit to one of his hotels. "It has been a tremendously successful project," Sanders said, "and he wanted to say hello and thank you to the employees for all their hard work.”

Trump arrived in Tokyo on Sunday morning, local time.

Prime Minister Abe planed to welcome the president with pomp and ceremony, as well as the 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. ("We’ll soon find out," Trump told reporters.)

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 rising professional golf star Matsuyama, will play at Kasumigaseki Country Club, site of the golf competition when Japan hosts the 2020 Olympics.

Trump expressed excitement about his round with Matsuyama, telling reporters that "he’s a great celebrity, a great athlete, he’s really got a lot things going, including the 'it factor.'"

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.