BEIJING - China will adhere to its family planning policy so as to maintain a low reproduction rate, said the country's family planning chief on Sunday, expected to be the eve of the world's population reaching seven billion.

"Over-population remains one of the major challenges to social and economic development," said Li Bin, director of the State Population and Family Planning Commission in an exclusive interview with Xinhua, adding that the population of China will hit 1.45 billion in 2020.

Li said maintaining and improving the existing family planning policy and keeping a low reproduction rate, along with addressing the issues of gender imbalance and an aging population, will be the major tasks in the future.

Li's words came just one day before Oct 31, the day on which the United Nations estimates the world's population will reach seven billion.

Zhai Zhenwu, a leading Chinese demographer, said earlier this week that China's family planning policy had postponed this day for at least five years, as it prevented 400 million people from being added to the country's population, which is 1.34 billion at present.

"The population of China would have hit 1.7 billion had it not been for the family planning policy, and it would have created difficulties for society," said Li.

The most populous nation in the world, China introduced its family planning policy, often referred to as the "one-child policy", in the late 1970s to curb pressure on the environment and resources.

Li said the policy has made a favorable environment for the country's economic development and social stability by alleviating demand for fundamentals including education, employment and housing.

Thanks to the policy, China's average education term has reached nine years and its population's life expectancy 73.5 years. In addition, maternal mortality rates and infant mortality rates are among the lowest in all developing countries.

"The Chinese government seriously fulfills the World Population Plan of Action and the Millennium Development Goals set by the United Nations, making positive contributions to the world's population development," said Li.

However, Li said that besides overpopulation, China is still facing other population-related challenges, including gender imbalance and an aging population.

For every 100 girls born in 2010, 118 boys were born. And 13.26 percent of China's population are aged 60 or above. It is expected the ratio will hit one third, or 440 million, by 2050. One fifth of the population will be 80 years of age or older in 2050, according to Li.