Guangdong, China's most populous province, has officially asked the central government for permission to relax the application of the country's family-planning policy and allow qualified local couples to have two children.

"The province has submitted an application to the central government and is now waiting for approval to be the leader in the country in the relaxation of the family-planning policy," said Zhang Feng, director of the Guangdong population and family-planning commission.

Couples in which either the husband or wife is an only child will be allowed to have a second child, Zhang said.

"I don't know whether the central government will give the green light to Guangdong or not, or when Guangdong's application will be approved, but the province now has room to relax the one-child policy, which has been in place for more than three decades," Zhang told local media on Sunday.

His remarks came a day before World Population Day, an event meant to draw attention to the difficulties caused by increases in population.

Zhang said Guangdong's birth rate has remained low for more than 10 years.

During the past decade, women living in Guangdong have given birth to 1.7 children on average.

According to official statistics, China's family-planning policy has averted more than 35 million births in Guangdong since it was introduced 30 years ago.

Zhang said relaxing the policy will not lead to a fast increase in population, largely because the cost of giving birth to children and raising them has increased in the province.

Xu Dongyin, a Guangzhou white-collar worker, said she will not consider having a second child, even if the province relaxes the family-planning policy in future.

"I don't think I can afford a second baby," said the 29-year-old woman, who has a one-year-old daughter. "The costs of housing and of bringing up a child are very high in Guangzhou.

"I think I'll have to set aside more than 1 million yuan ($154,560) to bring up my daughter and send her to study abroad after she graduates from a domestic college.

"And I think Guangdong's population will begin to decrease in one or two decades when many residents, especially urban residents, choose to have a DINK (dual income, no kids) family or refuse to have a second child."

Wang Chengyao, a resident in Guangzhou's Tianhe district, said he welcomes a policy change that will allow residents to have a second child, although Wang himself does not want to have one.

"The relaxed family-planning policy will certainly help in dealing with the difficulties brought about by having an older population in Guangdong," said Wang, who is in his 30s.

By the end of this past year, Guangdong was home to more than 10 million people older than 60, who accounted for about 10 percent of the province's total population. The elderly population there is increasing by 3.5 percent a year.

With more than 104.3 million residents, Guangdong recently surpassed Henan and Shandong provinces to become the most populous province in China. That figure is expected to reach 135 million by the end of 2015.

Guangdong, which contains 1.9 percent of China's total land area, now is home to 9 percent of the Chinese population.

In Guangzhou, capital of Guangdong, the population has exceeded 15 million and is projected to reach 18 million in 2020.