BEIJING - China will not loosen its one-child policy despite a top family-planning official's acknowledgment yesterday that the policy was partly to blame for a worsening surplus of boy babies and shortage of girls in the world's most populous nation.

In 2005 in China, 118 boys were born for every 100 girls. In some regions, the figure has reached 130 boys for every 100 girls; the average for industrialized countries is between 104 and 107 boys for every 100 girls.

Zhang Weiqing, minister of the National Population and Family Planning Commission, said the government was committed to ending the sex imbalance within 10 to 15 years with education campaigns, punishments for sex-selective abortions, and rewards - such as retirement pensions - for parents who have girls.

"This problem is a reality of country life in China," Zhang said. "We have a 2,000-year feudal history that considered men superior to women, that gave boys the right to carry on the family name, and allowed men to be emperors while women could not."

Zhang said China's basic policy, in effect since the late 1970s, was reviewed and renewed without change last month. The policy limits urban couples to one child and rural families to two to control the population and conserve natural resources. Beijing says it has helped prevent 400 million births and has aided the nation's rapid economic development.

Dropping restrictions on childbearing would risk a population surge as a baby-boomer generation born in the early 1980s begins starting families, Zhang said. Another factor in the government's decision is that many migrant workers living in cities have been evading restrictions and having two or more children, he said.

China has 1.3 billion people, 20 percent of the global total. Zhang said the government had pledged to keep the population under 1.36 billion by 2010 and under 1.45 billion by 2020.