Chinese couples in the 21st century could face even tougher birth control restrictions unless the current one-child policy is fully enforced, a population expert said.

China's average birthrate of 2.46 children for each woman still outstrips government targets despite strict family planning rules imposed in the 1970s, the China Daily quoted researcher Kong Deyong as saying.

"If China cannot keep its fertility rate under 2.16 before the year 2000, it will be difficult for each Chinese couple to even have 0.5 children in the next century," Kong said.