President Xi Jinping said Wednesday China must adhere to the basic state policy of family planning in the long term.

"The population issue has always been an overall, long-term, strategic issue facing our country," said Xi in a written instruction to the Family Planning Association conference in Beijing.

"For some time in the future, China's basic national condition of a large population will not fundamentally change. It will continue to put pressure on economic and social development. Tensions between the size of the population and resources and environment will not fundamentally change," said Xi, who is also general secretary of the Communist Party of China Central Committee.

Xi spoke highly of the efforts of the Family Planning Association over the years, adding that it should earnestly perform its duties, help people understand the adjustments to the family planning policy, and provide relevant services.

China's family planning policy, which was introduced in the 1970s, limited most urban couples to having one child. Starting 2016, China has allowed all married couples to have two children. This follows an earlier easing of the policy in 2013 allowing couples to have a second child if either parent is an only child.

In the next 15 years, China's  working-age population is projected to shrink to 56.9 percent of the total population in 2030, according to new data provided by the Population and Development Studies Center at the Renmin University of China.