TOKYO (AFP) - The biggest crowds of his nearly three-decade reign thronged Japan's Imperial Palace on Friday (Dec 23) to celebrate Emperor Akihito's 83rd birthday on what could be his last such appearance after expressing his desire to abdicate.

It was his first birthday since he announced in August that his advancing age and weakening health mean he may no longer be able to carry out his duties, setting the stage for Japan to prepare for an historic abdication.

The Imperial Palace said some 33,300 people - the biggest crowd since Emperor Akihito ascended to the throne in 1989 - attended his birthday address, waving small Japanese flags as crowds shouted "Banzai" or "Long live".

Deliberations over his retirement wish are under way in an advisory panel set up by Prime Minster Shinzo Abe in September to study a possible legal mechanism for a royal departure, which currently does not exist.

Any eventual move by Emperor Akihito to step down, which would see him replaced by his eldest son Crown Prince Naruhito, appears to have wide support, according to recent opinion polls.

Speculation about his future emerged earlier this year with reports that he had told confidantes that he would like to step down in a few years, in what would be the first abdication from the Chrysanthemum Throne in two centuries.

He has keenly embraced the role of symbol of the state imposed after World War II ended. Previous emperors including his father, Hirohito, had been treated as semi-divine.