China's sustainable development faces greater challenges ranging from a fragile natural ecological environment to resource constraints, senior Chinese officials said ahead of the United Nations Conference on Sustainable Development to be held in Rio de Janeiro.

A national report released on Friday to set out the country's stance on sustainable development said that apart from eastern coastal areas, most regions of China are still in the middle or early stage of industrialization and urbanization.

Around 122 million people live in poverty in China, according to the country's new rural poverty line set last year. China has the largest aging population in the world, more than 100 million, with low-level social security.

China's per capita fresh water accounts for 28 percent of the global average, arable land, 40 percent, and forest resources, 25 percent.

Per capita recoverable reserves of oil are 7.7 percent of the world's average, and reserves of iron ore and copper are both 17 percent.

"Rio+20 is a reminder for Chinese policymakers at all levels that time waits for no one in the race against a fast-deteriorating environment," said Yong Rong, who heads Greenpeace East Asia's political and public affairs unit.

One in every four people in China now has to drink substandard tap water, and environmental disasters cost the country 2.6 trillion yuan ($428 billion) in losses last year, she said.

"What is missing is not strong political will from Beijing but concrete action at lower levels that will lead to actual changes," Yong said.

The report came less than three weeks before the United Nations Conference on Sustainable Development, also known as Rio+20.

The event is expected to attract about 135 heads of state and up to 50,000 participants, including government officials, and participants from the private sector and non-governmental organizations, who will discuss how to reduce poverty and promote social equity and environmental protection.

"The conference shall send a positive, clear and powerful message to reinvigorate international cooperation ... strengthen the pillar development role of the UN and inject new vitality into global sustainable development," said the report.

After a few rounds of closed-door negotiations, negotiators from over 190 countries and regions have yet to reach a consensus on a draft action plan, which has to be ready for approval by the time world leaders arrive in Rio de Janeiro for the three-day summit starting on June 20.

"All participants should show the sufficient political will ... make concerted efforts and reach a consensus as early as possible instead of postpone serious issues and problems to the last stage of the meeting," said Du Ying, vice-minister of the National Development and Reform Commission, who is also head of the preparatory committee of the Chinese delegation.

Sustainable development means meeting the needs of the present without compromising the ability of future generations to meet their own needs. It consists of three pillars — economic development, social development and environmental protection.

The Rio meeting should adhere to the principle of "common but differentiated responsibilities", said Du.

Developing economies, especially the least developed economies, lack the ability to cope with issues such as food security, resource constraints, climate change and public health safety. However, developed economies are less willing to honor their commitments due to the economic downturn.

Commenting on the commitment to the three pillars, Du said it is necessary to put people first and ensure the sustainability of resources and the environment.

China incorporated sustainable development into its national strategies in 1996 and proposed the scientific outlook on development in 2003.