China faces a population surge in the next five years and the government will enforce "one-child" policies to keep the country's numbers at 1.37 billion by 2010, China's top population official said.

"In the next five years, China will face its fourth upsurge of births, and we must stabilise and improve the current family planning policies and hold to a stable, low birth-rate," Zhang Weiqing, the minister in charge of the National Population and Family Planning Commission, told a meeting in Beijing on Friday.

China's official population at the start of 2005 was 1.3 billion. China experienced several birth peaks from the 1950s to the 1980s.

Zhang said China's three decades-old restrictions on family size, which generally restrict most urban couples to one child and rural couples to two, are under challenge by new forces.

"The public's fertility preferences and behaviour are increasingly diverse, and the children of one-child families are entering their marriage and child-rearing phase," Zhang said in his speech that appeared in the state-run press yesterday.

But Zhang dismissed recent discussion among Chinese experts and even officials about easing some of the country's restrictions on family size, especially in cities.

In recent years, demographers and some local governments across China have proposed trial adjustments to China's national family planning policies, often in response to the growing number of affluent urban Chinese who choose not to have any children.

Zhang said that any family-planning policy changes must first receive the approval of China's State Council - China's cabinet.

In the 1970s and 1980s, China progressively introduced restrictions on the number of children couples are allowed.

While nearly all urban couples abide by the "one-child" restriction, in the countryside many couples have more than two children, despite the threat of heavy fines and forced abortions.

But Zhang also said China is troubled by a "prematurely aging" urban population and a major imbalance in numbers of boys and girls born to rural couples - problems that are at least partly an outcome of its birth restrictions.

More than 10 per cent of the 1.3 billion people in the world's most populous country were 60 or above, Chinese officials said in October.

China has warned that the already strained social security and pension systems must be reformed before the elderly population is expected to peak by the end of the 2020s.

Official statistics indicate that 119 boys are born for every 100 girls, because some tradition-minded rural families abort female foetuses to ensure they can have at least one boy.