Japan's Emperor Akihito has expressed his desire to abdicate in the next few years, public broadcaster NHK reports.
The 82-year-old, who has had health problems in recent years, reportedly does not wish to remain emperor if he has to reduce his official duties.
But a palace spokesman denied that there is any official plan for the monarch to abdicate in what would be an unprecedented move in modern Japan.
Crown Prince Naruhito, 56, is next in line to the Chrysanthemum Throne.
An unnamed government source told Japan's Kyodo news agency that the emperor, who plays a largely ceremonial role but is respected deeply by many Japanese, has been contemplating the move for about a year.
His family had accepted his decision, an unnamed palace source told NHK.
However, both palace and government sources say the Imperial Household Law would have to revised to allow for the abdication to take place.
A change to the Imperial Household Law, which stipulates the rules of succession, would require approval by Japan's parliament.
Despite a categorical denial of the reports by imperial palace spokesman Shinichiro Yamamoto, the emperor's reported wishes are being given prominent attention in the Japanese media.
Emperor Akihito has been admired for distancing the monarchy from its association with the aggressive nationalism of World War Two.
In 1989 he succeeded his father, Hirohito, who had had the status of a living god in Japan until he was stripped of that role by the victorious Americans who wrote the country's post-war constitution.
Emperor Akihito had surgery for prostate cancer in 2003 and a heart bypass operation four years ago.
In 2011, he took the highly unusual step of making a televised national address following the devastating earthquake and tsunami at Fukushima.
Five things about Japan's emperor:
- Has adopted a more modern style, making efforts to draw the imperial family closer to the people.
- He married a commoner in 1959 - their love story captured the nation and was dubbed the "tennis court romance" as they met over the nets. Together he and Empress Michiko have three children.
- Has sought to heal the scars of WWII, saying last year: "Looking back at the past, together with deep remorse over the war, I pray that this tragedy of war will not be repeated and together with the people express my deep condolences for those who fell in battle and in the ravages of war."
- Acknowledged his Korean ancestry in the run-up to the 2002 World Cup, which Japan and South Korea jointly hosted. This surprised many in Japan given the country's bitter colonial legacy on the Korean peninsula.
- His passion is marine biology and he is an expert on the goby fish.