TOKYO - JAPAN'S crown princess Masako is grateful she has been able to increase her official duties in the past year while trying to recover from a mental disorder, she said in a statement issued for her birthday.

'Although I feel regret for not been able to fully recover yet, I am grateful that I have been able to extend the scope of activities in the past one year,' said the princess, who turned 44 on Sunday.

Princess Masako, once a lively career diplomat, has been largely absent from the public eye for more than three years, suffering from a mental disorder that officials have attributed to the stress of adjusting to life in the imperial palace.

The princess said in the statement she hoped her six-year-old daughter, Aiko, the only child with her husband, the Crown Prince Naruhito, will enthusiastically take a new step as she enters an elementary school next April.

Royal watchers have said pressure to bear a male heir was a major cause of her illness. -- REUTERS