Melania was welcomed by Akie Abe, the wife of Japanese Prime Minister Shinzo Abe, at Mikimoto's flagship pearl shop as part of her cultural programmes, while dozens of security guards kept close watch.

The two greeted and kissed each other on the cheek instead of shaking hands or bowing.

Then they went upstairs to a "hidden floor" of the building, reserved for VIPs, to talk over tea and coffee. No details of their discussions were released.

Mikimoto brought in two "ama" divers who traditionally harvest pearls, clad in typical white costumes with big goggles and wooden buckets, to explain pearl farming to the US First Lady.

Japan is known for producing especially high-quality pearls.

"Wonderful visit w/ Mrs. Abe today! Enjoyed conversation over tea & the cultural presentation on the history of pearls," Melania tweeted after the meeting.

One of the divers, 57-year-old Miaki Okumura, told reporters after the two VIPs left the shop: "I was asked how deep the waters we dive are, and how long I can hold my breath."

"I answered that the depth was about five-six metres and I can hold my breath for about 40-50 seconds," she said, adding that Melania Trump seemed impressed at her endurance.

"She looked like a very kind person and was also very beautiful. Her hands were beautiful and warm when we shook hands."

The other diver Saki Satonaka, 22, said Melania Trump "congratulated me for my debut as a professional ama diver a month ago."

"I'll keep the wonderful memory of today's event throughout my life," Satonaka said.

Melania posed with Akie and the divers for photos but made no comment to the press. The pair also watched an educational video on cultivated pearls.

In the old days ama divers, the majority of whom are women, played an essential role in collecting pearl oysters in the sea.

The firm was founded in 1899 after Kokichi Mikimoto, known as the pearl king, succeeded in cultivating pearls for the first time in the world in 1893 in the western prefecture of Mie.