Donald Trump became the first foreign leader to meet with Japan's newly enthroned Emperor Naruhito, an honor Prime Minister Shinzo Abe hopes will help charm the U.S. president when it comes to thorny trade talks.

Trump was greeted by the new emperor and his wife at the imperial palace in Tokyo on Monday as part of a formal welcoming ceremony broadcast live on national television.

The president made it clear he was pleased to have been given the honor of the first reception with the emperor, who is treating him and his wife Melania Trump to a lavish state dinner later.

"It's over 200 years since something like this has happened. So it's a great honor to be representing the United States," Trump said at a dinner with Abe and the leaders' wives on Sunday.

The meeting was the main event in a feel-good trip that started Saturday and has seen Abe and Trump playing golf, eating out, watching sumo and generally enjoying an all-Japanese weekend.

Abe hoped those good vibes will spread into talks on trade, military ties, the stumbling efforts to rein in the Democratic People's Republic of Korea (DPRK)'s nuclear weapons program, and a growing superpower rivalry between Washington and Beijing.

Within an hour of touching down in Tokyo, Trump railed against what he sees as a trade imbalance between the world's top and third-largest economies and vowed to make the relationship "a little bit more fair."

But on Sunday, Trump struck a softer note, saying that "much" of that deal would wait until Abe faces upper house elections likely in July as rumors swirl that the popular prime minister will combine that vote with a snap general election.

'Small weapons'

On the DPRK, Trump appeared to undercut his own national security adviser, the hawkish John Bolton, by downplaying two recent short-range missile tests by DPRK leader Kim Jong Un which raised tensions in the region.

"North Korea (DPRK) fired off some small weapons, which disturbed some of my people, and others, but not me," Trump tweeted.

"I have confidence that Chairman Kim will keep his promise to me."

Before Trump landed in Tokyo, Bolton had told reporters there was "no doubt" that the launches contravened UN Security Council resolutions, in the first such statement by a senior U.S. administration official.

The issue is bound to come up as the leaders meet families of people abducted by the DPRK during the Cold War era to train Pyongyang's spies, an emotive issue in Japan that Abe has pressed Trump to raise in talks with Kim.

Abe himself has frequently offered to meet Kim to solve the "abductee problem," as it is known in Japan.

On Tuesday, Trump is expected to address troops at a U.S. base in Japan, highlighting the military alliance between the two allies.

His visit there will underline another big U.S. priority -arms sales to Japan, which is considering revamping its air force with advanced U.S. F-35 warplanes.