BEIJING - A bill submitted to China's top legislature for deliberation aims to allow couples to have two children if either parent is an only child.

The State Council, China's cabinet, submitted the bill on adjusting and improving the family planning policy to the bi-monthly session of the Standing Committee of the National People's Congress (NPC), which runs from Monday through Saturday.

The new one-child policy is expected to go into force in some provincial regions in the first quarter of 2014, said Yang Wenzhuang of the National Health and Family Planning Commission, adding that health and family planning authorities at various levels are conducting risk assessment for the policy.

They are still calculating the number of such couples and their situations before specific regulations are approved by provincial peoples' congresses, the official said.

The State Council argues adjustment to the policy in the face of a steadily declining birth rate and changing demographics.

The birth rate has remained relatively low and shows a tendency to fall further. The rate has dropped to between 1.5 and 1.6 since the 1990s, which means each Chinese woman of child-bearing age gives birth to 1.5 to 1.6 children on average. The working population began to drop in 2012 by 3.45 million annually, and it is likely to fall by 8 million each year after 2023.

The population aged 60 and above will reach 400 million and account for one-fourth of the total population in the early 2030s, up from one-seventh now.

"If the current family planning policy persists, the birth rate will continue to fall and lead to a sharp drop of the total population after reaching a peak," said Li Bin, minister in charge of the National Health and Family Planning Commission, when briefing lawmakers.

The sex ratio at birth has been over 115, (115 boys vs 100 girls), in the past two decades and in 2012 it reached 117.7. A ratio between 100 and 107 is considered normal.

"It is the right time to make changes. The low birth rate is stable, the working population still large and the burden of supporting the elderly remains relatively light," she said.

The State Council suggests that provincial congresses and their standing committees amend local family planning regulations after evaluation of local demographics.

An increase in births is expected if the policy changes but will not seriously affect the food supply, public education, healthcare or employment, Li said.

China's food safety and public service schemes are designed to meet the needs of 1.43 billion population in 2020 and 1.5 billion in 2033. Even with the policy change, the total population will not exceed 1.38 billion in 2015, Li said.

Family planning must continue, since a large population remains a major obstruction to realizing comprehensive, balanced and sustainable development.

Local authorities are expected to implement the family planning policy, improve people's awareness and punish those who violate the policy.