The public pension fund may sell Japanese government bonds this year to cover payments to retirees.

The Government Pension Investment Fund is the world's largest, boasting about ¥120 trillion in reserves. It has also been the biggest buyer of Japanese bonds.

"The big change this year for us is that there is zero new money to invest, so we may need to be a seller in the market to meet the pension benefits," President Takahiro Kawase, 67, said Tuesday.