BEIJING -- China's social security fund manager on Friday warned of a "huge capital gap" amid future waves of pension payments to retirees as the country enters a period of rapid aging.

"The current size of the social security fund fails to match China's  gross economic scale and is far from the level that can fill the gap in the pension fund balance," Dai Xianglong, chairman of the National Council for Social Security Fund (NCSSF), said at a forum held here Friday.

Dai did not reveal the exact capital deficit figure, but his warning came as the country's regulators are considering allowing the fund to invest in the equity market for higher yields.

By the end of last year, some 123 million Chinese, or about 9.1 percent of the nation's population, were aged over 65, and the ratio of working-aged Chinese to the country's seniors will drop from 10:1 in 2000 to 2.8:1 in 2050, according to data released by the Health Aging Symposium last month.

Founded in 2000, the social security fund managed by the NCSSF is designed to serve as a solution for the country's aging problem as well as a strategic reserve to support future social security expenditures.

The assets of the social security fund reached 868.84 billion yuan ($137.91 billion) at the end of last year, compared with the country's 10.8-trillion-yuan gross domestic product.

"Facing an accelerating aging process in China, the pension fund is under increasing pressure to make ends meet," Dai said, "and this trend is going to last for a long time."

Dai suggested appropriating more state-owned assets into the social security fund and using the fund in more investment sectors to protect its value from inflation.

In 2011, the fund's investment income stood at 43.1 billion yuan, with a yield rate of 5.58 percent.