Japanese Crown Prince Naruhito turned 57 on Thursday saying he is ready to become emperor after his father Akihito, who could abdicate as soon as next year, and that like him, he will be an emperor who "shares the pain and joy of the people".

A government panel is debating how to allow the 83-year-old Akihito, who has had heart surgery and prostate cancer treatment, to step down after he said in August that he feared age might make it hard for him to fulfil his duties.

The last time an emperor abdicated was in 1817 and current law does not allow it.

In January, media reports said the government was considering steps that would allow Akihito to abdicate and for Naruhito to ascend the throne on Jan. 1, 2019. The government could submit a special abdication law to parliament as early as this spring.

Naruhito told reporters he was "profoundly moved" when Akihito suggested he would like to step down.

"I accept the emperor's thinking with sincerity and will bear it in mind all the time as I carry out my duties," Naruhito said.

He added that he would continue in the footsteps of Akihito, who has worked hard to heal the wounds of World War Two, waged in the name of his father, Emperor Hirohito.

"As a symbol of the state and the people of Japan, I will share their pain and their joys, praying for their happiness," Naruhito said.

The prince, who married former diplomat Masako Owada, has one daughter, 15-year-old Aiko, who is not allowed to ascend the throne because female inheritance is not permitted. Naruhito is followed in the succession by his brother, Prince Akishino, and Akishino's 10-year-old son, Hisahito.

Photos of the family released to commemorate Naruhito's birthday show him sitting formally with Masako and Aiko, who appears to be very thin.

An Imperial Household Agency spokesman said there was nothing special to announce about Aiko's health, but the Crown Prince touched on a period last autumn when Aiko was absent from school for some six weeks.

"For a time she was unwell, which caused some worry, but thanks to support from her mother, she has now returned to her usual school life," Naruhito said.