Kirk Spitzer

USA TODAY

TOKYO — Japan’s ailing Emperor Akihito plans to deliver a rare television message to the nation Monday, when he may indicate that it’s time for him to step down from the world’s longest-running hereditary monarchy.

Taking that step may not be easy, however. No Japanese monarch has abdicated in nearly 200 years, no law governs such cases, and the popular 82-year-old monarch’s retirement could raise delicate questions about a ban on female succession and the imperial family’s place in society.

Akihito has been in poor health in recent years and has cut back on a busy schedule that includes public appearances and goodwill missions across Japan and the Asia-Pacific region.

News reports last month that Akihito would like to abdicate in favor of his son, Crown Prince Naruhito, 56, set off a round of hand-wringing throughout Japan.

Under Japan’s post-World War II constitution, the emperor is “the symbol of the state and of the unity of the people,” but he has no governmental authority and is not permitted to take part in political activity.

Akihito, the 125th emperor of Japan, acceded to the Chrysanthemum Throne in January 1989, at age 55, following the death of his father, Emperor Hirohito, who led Japan during the country’s harsh colonial era and the world war that followed.

Akihito and Empress Michiko are venerated by the Japanese, and the imperial family remains a popular institution. The emperor’s birthday — Dec. 23 — is a national holiday, when tens of thousands of well-wishers gather outside the Imperial Palace to greet the royal couple.

The imperial family traces an unbroken male line dating back at least 1,500 years. The government briefly discussed revising the law in 2005 to permit women to succeed to the throne if there were no male successors, but the effort was strongly opposed by traditionalists and the matter was dropped.

Japanese national broadcaster NHK reported last month that Akihito had informed the Imperial Household Agency, which manages the emperor’s affairs, that he wished to abdicate “in a few years” because of medical problems that have included prostate cancer and heart surgery.

According to Japan’s Kyodo News service, Akihito is likely to avoid direct mention of abdication during his televised message, since that could require changes to the constitution or Imperial Household Law. Any direct discussion of the issue by the emperor could be construed as improper participation in government policy-making.

Instead, Akihito is expected to discuss his thoughts on his role as emperor and concerns that he may not be able to fulfill his official duties in the future, the news service said.

The taped message is scheduled to air at 3 p.m. Monday (2 a.m. ET Monday), after financial markets close.

The address will be just the second time Akihito has delivered a nationwide TV address. The first was after the devastating earthquake and tsunami that struck northeast Japan in March 2011. Many Japanese found his message of sympathy for nearly 20,000 people killed or missing and reassurances to the nation to be deeply moving.