Arrangements are believed to be underway for US Vice President Mike Pence to visit Japan in October to attend the enthronement ceremony of Emperor Naruhito.
US officials and other sources say that the US government is preparing for Pence to attend the October 22 event. It serves as a formal announcement for the accession that took place in May.
Pence's most recent visit to Japan was in November last year.
As chairman of the US National Space Council, Pence is also expected to hold talks with Japanese officials about cooperation between the two countries' space programs. The US is working on plans to send astronauts to the Moon and Mars.
Analysts say Pence's visit will reaffirm strong ties between the allies. President Donald Trump was the first state guest of the new Reiwa era.