TOKYO - JAPAN'S Crown Prince Naruhito, celebrating his birthday on Monday, said he was pleased his reclusive wife, who has been suffering from stress-induced illness, is now able to carry out more public duties.
But he expressed concerns for the health of Emperor Akihito, who had surgery for prostate cancer in 2003.
Ms Masako, 45, has skipped most public duties over the past five years because of her illness as the former career diplomat struggled to adjust to life inside the world's oldest monarchy.
In a sign of her recovery, the princess this year played a full part in the traditional New Year greetings at the palace, central Tokyo, where tens of thousands of well-wishers gathered.
'Masako and I are both pleased that she is becoming able to carry out public duties that she could not before,' the prince told reporters ahead of his 49th birthday.
But Prince Naruhito, speaking on Friday, said she must not push herself when she is in good health as it could hamper her progress.
'Her doctor has told me that she needs to take careful steps so that her condition does not regress by pushing herself too hard,' the prince said, adding she should be 'in no hurry' to make her full return to official duties.
The doctor has also said it would be desirable for the princess to find her 'life work' in addition to bringing up children, he said. Meanwhile, Prince Naruhito said he would do what he could to ease his father's anxieties.
Doctors said in December that they had found traces of bleeding in the 75-year-old emperor's stomach, partly due to stress. The Imperial Household Agency said last month the emperor and empress would lighten their official duties for health reasons.
'I hope from my heart that the emperor's anxiety would be eased, and we will do what we can do for that,' the prince said. Prince Naruhito declined to comment on the looming succession crisis in the 2,000-year-old monarchy.
Ms Masako was under intense pressure to bear a son under Japan's male-only royal succession law. Ms Masako and Prince Naruhito have one child, seven-year-old Princess Aiko, while his younger brother has a two-year-old boy, the first prince born to the royal family in 40 years.
Experts say a single boy is not enough to give the imperial line long-term security. The other children in the broader imperial family are female and will become commoners upon marriage.