President Trump on Sunday discussed trade and North Korea problems over golf and dinner with Japanese Prime Minister Shinzo Abe, as a prologue to the most critical stretch of the president’s 12-day Asia trip that starts Monday with formal talks in Tokyo.

“We are in the midst of discussions on many subjects, including North Korea and trade and other things,” Trump said before the dinner in Tokyo with first lady Melania Trump and Abe’s wife, Akie Abe. “But time is a little bit limited. Tomorrow’s a busy day.”

To be sure, formal talks between Trump and Abe, who appear to have a solid diplomatic relationship, begin in Tokyo with tensions running high about North Korea. The two world leaders are expected to focus on how to present a united front to stop North Korea’s pursuit of a nuclear arsenal -- made clear recently by leader Kim Jong Un’s repeated nuclear and ballistic-missile tests.

Trump will be looking for Japan to limit trade with neighboring North Korea, to squeeze the rogue nation economically, while Abe wants reassurances that the United States will stand by its treaty obligations to defend Japan if attacked.

After visiting Japan, Trump then travels to South Korea, China, Vietnam and the Philippines.

Sunday’s casual lunch, nine holes of golf at the Kasumigaseki Country Club and the dinner will give way Monday to formal talks, a press conference and a state dinner.

Eager to forge a bond with Tokyo's crucial ally, Abe was one of the first world leaders to court President-elect Donald Trump. He was the first to call Trump after the election, and rushed to New York days later to meet the president-elect and present him with a pricey, gold Honma golf driver.

The two men also met on the sidelines of an international summit in Italy this spring and Trump hosted Abe in Florida. White House officials said Trump has spoken with Abe by phone more than any world leader, aside from British Prime Minister Theresa May.

That bond was clear on Sunday.

"The relationship is really extraordinary,” Trump also said Sunday before the dinner. “We like each other, and our countries like each other."

When Trump hosted Abe in Palm Beach earlier this year, they played at one of Trump's Florida golf courses. For that outing, Trump brought along pro golfer Ernie Els, so this time Abe matched him by bringing along Japanese pro Hideki Matsuyama, who Trump described on the plane ride to Asia as "probably the greatest player in the history of Japan."

Before the game, Trump delivered a speech in which he hailed Japan as a "crucial ally" and warned adversaries not to test America's resolve.

"Japan is a treasured partner and crucial ally of the United States and today we thank them for welcoming us and for decades of wonderful friendship between our two nations," Trump told American and Japanese service members at Yokota Air Base on the outskirts of Tokyo, after arriving from Hawaii, his first stop on the trip.

Though Trump did not mention North Korea by name during the speech, the specter of its weapons program will loom large throughout Trump's five-nation trip. The president warned of the consequences of crossing what he called the "most fearsome fighting force in the history of our world."

"Together with our allies, America's warriors are prepared to defend our nation using the full range of our unmatched capabilities. No one — no dictator, no regime and no nation — should underestimate, ever, American resolve," he told the troops.

And while there is worry in the region about Trump's unpredictable response to the threat posed by Kim, Trump made clear he did not intend to tone down his bellicose rhetoric -- including dubbing Kim "Little Rocket Man" -- even while in an Asian capital within reach of the North Korea dictator's missiles.

"There's been 25 years of total weakness, so we are taking a very much different approach," he said, speaking to reporters on Air Force One.

Trump also will meet with Russian President Vladimir Putin on the sidelines of an upcoming summit in Vietnam.

The easy rapport with Japan could be strained if Trump takes an aggressive approach on trade or the two men disagree on how best to approach the threat looming in Pyongyang. During his campaign, Trump suggested Japan should acquire its own nuclear weapons to defend itself, hinted the U.S. might not come to the nation's defense, and accused Japan of "killing us" on trade. He has dropped that antagonist language almost entirely since the election, but tensions remain.

Scott Seaman, a director for Asia of the Eurasia Group, a political risk consultant organization, noted: "everything is fine with Trump until you tell him no. So far, Abe hasn't told him no."

The Associated Press contributed to this report.