People watch a large screen showing Japanese Emperor Akihito's video address in Tokyo, Japan, August 8, 2016. [Photo/Agencies]

TOKYO - Japanese Emperor Akihito, 82, in a rare video address to the public on Monday, said he worried that age may make it difficult for him to fully carry out his duties, remarks widely seen as suggesting he wants to abdicate.

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 - which would be unprecedented in modern Japan.

Once considered divine, the emperor is defined in the constitution as a symbol of the state and the unity of the people. He has no political power.

Akihito stopped short of saying outright that he wanted to abdicate, which could be interpreted as interfering in politics.

"When I consider that my fitness level is gradually declining, I am worried that it may become difficult for me to carry out my duties as the symbol of the state with my whole being, as I have done until now," he said.

Akihito took the throne after the death in 1989 of his father, Hirohito, in whose name Japan fought World War Two. He has sought to soothe the wounds of the war in Asia during trips overseas and tried to bring the monarchy closer to the people.

Akihito feels strongly that an emperor's full performance of his duties is integral to his constitutional role, experts say.

Opinion polls show the vast majority of ordinary Japanese sympathise with the emperor's desire to retire, but such a step would need changes to the law.

Akihito has been cutting back on official duties, with his heir, 56-year-old Crown Prince Naruhito, taking his place. There were limits to how far that could go, he said on Monday.