China will probably introduce an overall two-child policy in one or two years, senior demographers expect, as the top population authority said the government would keep fine-tuning birth rules to ensure a sustainable and balanced population growth.

Yang Wenzhuang, director of the family planning grassroots guidance department under the National Health and Family Planning Commission, said the relaxation of the family planning policy in 2013, which allows couples with one spouse being an only child to have a second child, helped lay a solid foundation for future adjustments to the birth rules.

The number of couples who qualify is about 11 million, with nearly 70 percent of them born after 1980, Yang said.