Japanese Emperor Akihito has expressed his desire to step down within "several years", national broadcaster NHK reported yesterday.

The 82-year-old monarch, who has had health problems in recent years, reportedly wants to retire if he is unable to fulfil his official duties under the Constitution. On the eve of his birthday last December, he had lamented that "my old age has caused me to make small mistakes at official ceremonies".

In May, the Imperial Household Agency announced changes to lighten the load on the Emperor and Empress Michiko, 81.

These included cutting down on the number of meetings with guests to the Imperial Palace.

The NHK, quoting unidentified sources at the agency, said the Emperor - who ascended the throne in 1989 when his father died - has made this desire known to his wife and children, Crown Prince Naruhito, 56, and Prince Akishino, 50.

The Crown Prince is next in line to the throne. He is married to Crown Princess Masako, 52, and they have one daughter, Princess Aiko, 14.

But under the Imperial Household Law that governs the status of the emperor, there are no legal provisions for the monarch to step down, the NHK said. This means changes to the law must be made to allow for his abdication, which will be Japan's first since Emperor Kokaku did so in 1817.

Emperor Akihito is the first emperor to serve a purely symbolic role under the post-war pacifist Constitution, which calls him a "symbol of the state and of the unity of the people".

His father was the wartime Emperor Hirohito, who had been regarded as a demi-god by the Japanese when the country waged war across Asia.

Emperor Akihito is the first monarch in Japan to marry a commoner. In a speech last August to mark the 70th anniversary of the end of World War II, he expressed "deep remorse" over Japan's actions.