Trump repeated his mantra the "era of strategic patience" with North Korea was over, and said the two countries were working to counter the "dangerous aggressions". Like Trump, he takes a hard-line position on North Korea, which helped him emerge victorious from a recent snap election in Japan.
Standing next to Japanese Prime Minister Shinzo Abe, Trump promised to work in solidarity with Japan to confront "the North Korean menace".
President Trump said on Monday that Japan could protect itself from a nuclear-armed North Korea by buying billions of dollars of American military equipment, drawing an explicit link between trade and security as he began a complex, politically charged tour of Asia. "And we make the best military equipment by far".
"For the last many decades, Japan has been winning, you do know that", Trump told a gathering of business leaders here.
At an afternoon news conference with Abe in Tokyo, Trump declared, "the era of strategic patience is over", and promised to counter "the risky aggressions" of the country led by Kim Jong-un, who the president has repeatedly called "Rocket Man".
Abe, for his part, publicly deflected questions about trade. But he railed against what he said were chronic trade imbalances with Japan. "We want fair and open trade, but right now our trade with Japan is not fair and it's not open".
Trump, as he told it, wasn't aware of the protocol against president-elects meeting with world leaders.
At first, Trump followed Abe's lead by gently spooning out small amounts of feed into the pond below.
Abe also called Trump his "dear friend" and hailed the benefits of what he called "golf diplomacy". "So I saw him and it worked out just fine", Trump recalled, saying, from that moment on, they'd been close.
The U.S. president is on the second day of a 12-day Asian trip that is focusing on North Korea's nuclear missile programmes and trade.