TOKYO — Japan’s rapid aging means the national population of 128 million will shrink by one-third by 2060 and seniors will account for 40 percent of people, placing a greater burden on the shrinking work force population to support the social security and tax systems.

The population estimate released today by the Health and Welfare Ministry paints a grim future.

In 2060, Japan will have 87 million people. The number of people 65 or older will nearly double to 40 percent, while the national work force of people between ages 15 and 65 will shrink to about half of the total population, according to the estimate, made by the National Institute of Population and Social Security Research.

The total fertility rate, or the expected number of children born per woman during lifetime, in 2060 is estimated at 1.35, down from 1.39 in 2010 — well below more than 2 needed to keep the country’s population from declining. But the average Japanese will continue to live longer. The average life expectancy for 2060 is projected at 90.93 for women, up from 86.39 in 2010, and 84.19 years for men, up from 79.64 years.

Experts say Japan’s population will keep losing 1 million every year in coming decades and the country urgently needs to overhaul its social security and tax system to reflect the demographic shift.