Japanese Emperor Akihito, 82, in a rare video address to the public, said on Monday that he worried that it might become difficult for him to carry out his duties fully due to his age.

Public broadcaster NHK reported last month that Akihito, who has had heart surgery and been treated for prostate cancer, wanted to step down in a few years - a move that would be unprecedented in modern Japan and for which no legal procedures exist.

Once considered divine, Japan's emperor is defined in the constitution as a symbol of the "unity of the people" and has no political power. While most ordinary Japanese sympathize with his desire to retire, conservatives who back Prime Minister Shinzo Abe are opposed to the move.