US President Donald Trump on Sunday played golf with Japanese Prime Minister Shinzo Abe and presented a trophy to the winner of a sumo tournament, turning to personal diplomacy for the second day of a Japan visit shadowed by tough trade talk.

Trump is unhappy with Japan's large trade surplus and is considering putting high tariffs on its auto exports if a bilateral trade agreement is not reached. 

But it was all smiles on Sunday as the two leaders played golf and later, with wives Melania and Akie, watched giant sumo wrestlers grapple on the final day of a 15-day tournament won by rising Japanese star Asanoyama.

Trump, the first US president to watch sumo in the sport's homeland, waved to the audience as he entered the hallowed Kokugikan and then saluted them with applause as they waved and raised their phones to take photos.

Arriving just in time for Asanoyama's bout, Trump nodded as Abe gestured in explanation, later watching as the three final wrestlers, wearing only traditional loincloths, lifted their legs high and stamped them to the ground in a ritual entrance.

The two couples used armchairs instead of sitting cross-legged on the "zabuton" cushions traditional for close ringside seats.

Trump, using a special set of wooden stairs fitted to the sumo ring, presented the 25-year-old Asanoyama with the President's Cup, a trophy topped with a bald eagle, the US national bird.

"In honor of your outstanding achievement as Sumo Grand Champion, I hereby award you the United States President's Cup," Trump said, reading from a prize certificate.

Security was tight, with fans forced to pass through metal detectors. The traditional throwing of cushions to mark an exciting round was prohibited.

The two met early at a suburban golf course. Trump, dressed in a red pullover, and Abe, wearing a blue blazer and white pants, smiled for photographers before taking off for their game, which took place in 30 degree Celsius temperatures as an unseasonal heat wave blasts Japan.

Abe's office later posted a "selfie" picture on the course with Trump and Abe smiling together, Trump wearing a red "USA" cap. Abe said in the post he hoped to make the Japan-US alliance "even more unshakeable."

Despite the bonhomie, trade was never far from mind.

"Great progress being made in our trade negotiations with Japan. Agriculture and beef heavily in play," Trump tweeted after arriving back in Tokyo from the suburban golf course where the two played 16 holes.

"Much will wait until after their July elections where I anticipate big numbers."