Emperor Akihito waves to well-wishers from the palace balcony in January. (Shizuo Kambayashi/AP)

Japan’s popular emperor, the 83-year-old Akihito, last summer asked the government to allow him to retire, an unprecedented step but one brought about, he said, by his inability to do the job to the fullest.

Japan’s cabinet took the first step Friday toward allowing him to abdicate — but not until the end of next year, when Akihito will be turning 85 and will have served 30 years on the Chrysanthemum Throne.

“The government is expecting the bill to be passed smoothly,” Yoshihide Suga, the chief cabinet secretary, told reporters Friday after the cabinet approved the bill to allow Akihito to retire and for his son, Crown Prince Naruhito, who is 57, to take over.

The bill will authorize the abdication as a one-time event rather than paving the way for future emperors to retire.

In a televised address last August, Akihito, who has had prostate cancer and heart problems, said that his health was declining and that he was “worried that it may become difficult for me to carry out my duties as the symbol of the state with my whole being.”

But because there was no legal provision to allow an emperor to abdicate, the Japanese parliament, known as the Diet, had to decide how to tackle the issue. Amending the Imperial Household Law would have taken years and created a precedent, so lawmakers drew up a special bill, which says that the Japanese public has “sympathy” for the emperor’s situation.

But the timing of the abdication still needs to be set, and Japanese media are reporting that it will probably take place at the end of 2018.

The abdication, the first in 200 years, is creating all sorts of headaches for protocol specialists in the Japanese government. The government had to decide what title to use for a retired emperor, and what to call the new era. The Japanese calendar uses years that coincide with the emperor’s reign, making 2017 the year Heisei 29.

Officials are also studying ceremonial practices from the past to figure out how to hold an abdication ceremony, the Kyodo news agency reported. The last emperor to retire was Kokaku in 1817.

The abdication comes at a time of intense speculation about the future of the imperial family and the strict rules imposed on it. Because women are not allowed to take the throne and because they become “commoners” after marriage, the family has shrunk to only 19 members and only four heirs. One is Akihito’s brother, also in his 80s, while Akihito’s sons are in their 50s.

The family is set to shrink further, to 18, after the announcement this week that Princess Mako, the emperor’s 25-year-old granddaughter, is about to be engaged to a university classmate, a lawyer and a commoner. Princess Mako’s brother, 10-year-old Hisahito, is the fourth heir to the throne and the only boy in his generation.

But Shinzo Abe, the Japanese prime minister, and his conservative Liberal Democratic Party have been resistant to any efforts to allow women to inherit the throne.

Japan’s emperors are said to be direct descendants of Amaterasu, the Shinto goddess of the sun, and are revered here. But the imperial system changed sharply when Japan was defeated in World War II. The U.S. occupying forces allowed Hirohito, Akihito’s father, to remain as emperor but reduced the position to that of a ceremonial figurehead.

The U.S.-written constitution imposed on Japan after the war said that the emperor would serve as a “symbol of the state and of the unity of the people” but would “not have powers related to government.”