US President Barack Obama charmed his Tokyo audience on Saturday with references to green tea ice cream, Japanese traditional hospitality and, of course, the small town that bears his name.

"I could not come here without sending my greetings and my gratitude to the citizens of Obama, Japan," said the president to the delight of the western Japan town that has turned its accidental fame into a cottage industry.

The ancient fishing town of 30,000, about 400 kilometres (250 miles) from Tokyo, has long supported its White House namesake, and some of its residents were in Tokyo to steal a glimpse of the president.

Wearing "I Love Obama" T-shirts, a small delegation braved rainy weather on a Tokyo sidewalk and waved as the presidential motorcade passed by.

"The president clearly looked at us and recognised us," said an excited Seiji Fujihara, who leads a dance troupe that on Friday performed a hula dance in honour of the president, who was born in Hawaii.

"I was so touched when President Obama mentioned our town," Fujihara gushed. "I felt goose bumps."

Obama in his speech Saturday recalled a childhood visit to Kamakura, a temple-studded town near Tokyo, where he "looked up at that centuries-old symbol of peace and tranquility, the great bronze Amida Buddha."

Then he quipped: "As a child, I was more focused on the matcha (green tea) ice cream. But I have never forgotten the warmth and hospitality that the Japanese people showed a young American far from home."

Obamania was alive and well among the audience -- where many hailed his personal charm and wide knowledge about the region.

"His voice was good. He spoke naturally. He has something that attracts people," said Yasuko Maki, a 60-year-old housewife.

Her husband, Akihiro, 66, agreed: "He covered every subject and explained how America will handle it. He intends to work as our partner. He is different from former US presidents."