TOKYO — Japan’s parliament on Friday passed a law allowing Emperor Akihito to become the country’s first monarch to abdicate in 200 years, but put off a debate over how to tackle the shrinking royal population and whether to allow women to ascend the throne.

In veiled language, the 83-year-old emperor expressed his wish to abdicate last August, citing his old age and health.

Under the law enacted Friday, his abdication must take place within three years.

Current succession rules allow only men from the paternal bloodline to ascend the 2,000-year-old Chrysanthemum Throne. Women, but not men, are forced to renounce their royal status if they marry a commoner.

Prime Minister Shinzo Abe’s conservative government supports male-only succession. Akihito’s son, 57-year-old Crown Prince Naruhito, is next in line.

Naruhito’s only child is a girl, and his younger brother, Prince Akishino, has two adult daughters and a 10-year-old son, Hisahito. This means only one of the emperor’s four grandchildren is an eligible heir.

After Naruhito’s daughter was born, a government panel discussed the possibility of allowing female ascension, but the talk quickly faded after Hisahito’s birth.