By Elaine Lies
TOKYO, Oct 22 (Reuters) - Japanese Emperor Naruhito is poised to officially proclaim his enthronement on Tuesday in a centuries-old ceremony attended by dignitaries, including heads of state and other royals, from more than 180 countries.
Naruhito, 59, and Empress Masako, a 55-year-old Harvard-educated former diplomat, took over in May in a brief, tradition-filled ceremony but Tuesday's "Sokui no Rei" is a more elaborate ritual in which he officially announces his change in status to the world.
Naruhito is the first Japanese emperor born after World War Two. He acceded to the throne when his father, Akihito, became the first Japanese monarch to abdicate in two centuries after worrying that advancing age might make it hard to perform official duties.
The celebratory mood for what has been proclaimed a special holiday has been tempered by Typhoon Hagibis, which tore through Japan 10 days ago. The typhoon killed at least 80 people and prompted the postponement of a planned celebratory parade.
Naruhito will wear a traditional robe and headdress to the ceremony, like his father did nearly three decades ago. It will start at 1:00 p.m. (0400 GMT) at the Imperial Palace's Matsu no ma, or Hall of Pine, the most prestigious space in the palace where he officially succeeded his father "with a sense of solemnity" on May 1.
He will declare his enthronement from the "Takamikura" - a 6.5 metre (21 feet) high pavilion that weighs about 8 tonnes - with an ancient sword and a jewel, two of the so-called Three Sacred Treasures, placed beside him.
Together with a mirror called Yata-no-Kagami, which is kept at the Ise Grand Shrine, the holiest site in Japan's Shinto religion, the three treasures comprise the regalia that symbolises the legitimacy of the emperor.
Empress Masako will also take part in the ceremony, wearing heavy traditional robes and having her own throne.
Emperor Akihito pledged during the previous ceremony in 1990 to observe Japan's pacifist constitution and fulfil his duty as a symbol of the state and of the unity of the people. Naruhito promised to follow his father's path before assuming the position and observers have noted he has so far made only small changes.
Naruhito's address will be followed by a congratulatory speech by Prime Minister Shinzo Abe, who will also lead three cheers for the new emperor to end the ceremony.
Among the expected guests are Britain's Prince Charles, who with then-wife Princess Diana attended Akihito's enthronement, as well as U.S. Transport Secretary Elaine Chao. Myanmar civilian leader Aung San Suu Kyi is also expected to take part.
A court banquet will be held on Tuesday night, and Emperor Naruhito and Empress Masako will host a tea party for foreign royalty on Wednesday afternoon.
The celebratory parade has been postponed until Nov. 10 while the government devotes its attention to coping with the aftermath of the typhoon. (Reporting by Elaine Lies; Editing by Paul Tait)