China acknowledges a relationship between its so-called "one-child policy" and a rising sex-ratio imbalance that threatens to leave tens of millions of Chinese men without wives. However, an official in charge of family planning policy says loosening the policy could allow China's already huge population to grow out of control. Daniel Schearf reports from Beijing.

China's top family planning official acknowledged Tuesday that Beijing's 33-year-old one-child policy is partly responsible for the country's mounting gender imbalance.

The policy limits most urban couples to one child, unless they themselves were single children, and rural couples to two children, if their first child is a girl.

The National Population and Family Planning Commission announced earlier this month that China's overall newborn gender ratio in 2005 was 118 boys to every 100 girls. In some regions, it is as high as 130-100.

Zhang Weiqing, director of the commission, told reporters Tuesday that Chinese tradition plays a role in the disproportionate number of male births.

"There are a lot of factors contributing to the imbalanced sex ratio. Chinese society has for several thousands of years traditionally preferred males. Secondly, in rural China, production levels are low, and China's social security system is not very sound," said Zhang.

Male children have traditionally been expected to look after their aged parents, and China's impoverished farmers, who receive little government help, want sons as old-age insurance.

Zhang acknowledged that modern technology is now used to ensure the birth of sons. Access to ultrasound has made it easy for many couples to determine the sex of a baby in the womb, and to abort female fetuses in the hope of later having a boy, thus contributing to the huge preponderance of male births.

The population commission's report said the resulting imbalance would mean that by the year 2020, the country would have 30 million more men than women, making it difficult for many men to find wives. The Chinese report called the gender imbalance a "hidden threat" that would threaten social stability.

China's youth are facing higher unemployment in the future, and experts worry that men who are both unemployed and unmarried could turn to crime.

Despite the problem, Zhang said regulations against multiple births are still necessary in order to prevent China's population, the highest in the world at an estimated 1.3 billion, from rocketing out of control.

Beijing maintains that the policy has prevented 400 million additional births.

China's official Xinhua News Agency reported Tuesday that the government has promised tough measures to prevent sex-selective abortion, but gave no specifics on the new measures.

The same situation exists in India, where, as in China, people traditionally prefer sons. The use of sex-selective abortions has also caused a huge imbalance in the sex ratio there, and the Indian legislature has made it illegal for doctors to tell prospective parents the sex of a fetus.

The Chinese government has offered cash incentives to rural girl-only families, to discourage abortions and abandonment of female children.

But, officials have used forced abortions and sterilizations in order to stay within prescribed birth quotas.