When world leaders gather in Rio de Janeiro, Brazil, on Wednesday for the United Nations Conference on Sustainable Development, or the Rio+20 as it is known, they need to demonstrate a strong political will and adopt concrete policies and measures to make the world a more sustainable place for future generations.

A follow-up to the 1992 Earth Summit, the biggest UN conference in years is expected to draw 50,000 participants from 190 countries. They will seek to address some of the major issues the world is facing today, including poverty reduction, environmental protection and social equity.

Compared to 20 years ago when countries adopted Agenda 21 - a blueprint for rethinking economic growth, promoting social equity and ensuring sustainability - key challenges ranging from climate change to the loss of biodiversity, and land degradation to water security have only become more alarming.

Contested issues at the summit include a set of sustainable development goals to succeed the UN's Millennium Development Goals due to expire in 2015, ways to promote the green economy and mustering funds for such development.

Whether to reaffirm the "common and differentiated responsibilities" agreed at the 1992 summit is a particularly contentious issue. The principle, designed to ensure that poor countries do not have to shoulder the same burden as rich countries in fixing the Earth's environmental problems, has served as the guideline for international cooperation and must be upheld if sustainable development is to be achieved.

The concerns and difficulties of developing countries can be alleviated if developed countries offer financial support and technology transfer, and provide market access for green products from developing countries.

China has made arduous efforts to promote sustainable development and eradicate poverty since the adoption of Agenda 21 and has made remarkable progress in social and economic development. Nevertheless, with more than 100 million Chinese residents still living in poverty, the country has much work to do.

Premier Wen Jiabao is scheduled to attend the summit and he will elaborate on China's approach to sustainable development. This testifies to China's support of the Rio summit and its expectation that the meeting will inject new vitality into global sustainable development.

As long as leaders adhere to the principle of common but differentiated responsibilities and determine priorities for attaining sustainable development goals that are supported by both political commitments at the highest level and action from top to bottom, the conference can produce real results.