BEIJING, May 6 (Xinhua) -- China's top family planning official Zhang Weiqing has voiced his concern that the country's current low birth rate may not be able to sustain as a result of widening wealth gap and early marriages in rural area, claiming that China is still facing risks of a "population rebound".

    "Early marriages are still prevailing in some parts of the country, especially in rural areas, which goes against the family planning policy," said Zhang, director of the National Population and Family Planning Commission (NPFPC).

    China's Constitution rules that men may marry at 22 and women at 20, while the country's family planning policy, which has been implemented since the 1970s, encourages late marriages and late childbearing, and limits most urban couples to one child and most rural couples to two.

    Zhang said, China's widening wealth gap is challenging the country's family planning efforts as its new-rich disdain the decades-old one-child policy to pay to have as many children as they like.

    The number of rich people and celebrities having more than one child is on a rapid increase, and nearly 10 percent of them even have three, according to a recent survey by the NPFPC.

    Zhang said, young couples, born in the 1970s and 1980s and raised as only children, now in their twenties and thirties, are allowed to have a second child, which also contributed to the rising birth rate in some central and western provinces.

    The NPFPC will continue to offer preferential services to couples following the family planning policy, Zhang said, adding the government's spending on family planning will be raised to 30 yuan (3.8 U.S. dollars) per person during the 11th five-year plan period (2006-2010).

    As the world's most populous nation, China has been following a strict family planning policy to contain its population growth.