President Joe Biden and Prime Minister Fumio Kishida unveiled the biggest ever upgrade in US-Japan defence ties on Wednesday during a lavish White House state visit.

Biden was rolling out the red carpet for Kishida with a luxurious dinner, plus music by legendary US singer Paul Simon, as he sought to underscore the importance of Japan as a crucial ally in the Asia-Pacific region.

"This is the most significant upgrade in our alliance since it was first established," Biden told a press conference with Kishida in the White House Rose Garden.

The US president, 81, said their relations were "unbreakable" and that their agreements on Wednesday set a "new benchmark for our military cooperation."

The two leaders unveiled plans to restructure the US military command in Japan, the biggest such change since the 1960s -- while the United States, Japan and Australia would also launch a joint air defence network.

The move is aimed at making US and Japanese forces more nimble in the event of a crisis.

Biden said the military upgrade was "purely defensive" and "not aimed at any one nation or a threat to the region."

Biden has made no bones about his desire to create alliances across the region.

On Thursday, he will host the first trilateral summit between Japan, the Philippines and the United States, aiming to deepen their alliances.

The pomp-filled state visit for Kishida was however also meant to underscore the broader cultural and economic relations between two allied nations who were at war 80 years ago.

Biden announced that a Japanese person will be the first non-American to walk on the Moon, flying on a US mission due to take place in a few years' time.

The leaders also announced deals for technology, including artificial intelligence and the economy. (AFP)