His comments came in a rare address to the public yesterday.
Emperor Akihito said: “When I consider my age of over 80, as well as my gradually deteriorating physical condition despite being luckily healthy at this moment, I am concerned about being able to fulfil my duties as a symbol with the utmost efforts, as I have done so far.”
He was speaking in a ten-minute recorded message broadcast on national TV.
Japan’s post-Second World War constitution restricts what the emperor can say as a symbolic monarch with no political power.
As expected, Akihito avoided explicit mention of abdication, which could have violated those restrictions.
Prime Minister Shinzo Abe said he takes seriously what Akihito said.
He said: “I think we have to thoroughly think what we can do to accommodate his concerns, taking into consideration the emperor’s age and the current burden of official duties.”
The monarch, 82, spoke publicly after recent media reports that he may want to abdicate because he did not want to cling to the title if his duties had to be severely reduced.
Abdication is not allowed under imperial law, largely inherited from the pre-war Constitution which banned the practice as a potential risk to political stability.
Reports said the government may consider a special law for one-time abdication for Akihito. The emperor suggested in his speech a need to consider how to make the succession process smoother.
His two sons have reportedly accepted the idea of an abdication. His elder son, Crown Prince Naruhito, is the likely successor.
The emperor normally speaks publicly twice a year, at a New Year’s speech at the Imperial Palace and to mark the end of the Second World War on 15 August.