UNITED NATIONS - UN Secretary General Ban Ki-moon on Monday called on international community to step up its efforts to address global development challenges.

The UN chief made the remarks at the opening of the UN General Assembly Special Session on the 20th anniversary of the International Conference on Population and Development (ICPD).

"As we celebrate the twentieth anniversary of the Cairo conference and look ahead to future, we cannot afford to short- change development," he said.

Poverty, basic human rights, as well as major demographic trends, including urbanization, migration, population aging, are some of the challenges the world needs to confront in order to achieve sustainable growth, Ban said.

He called for greater efforts to achieve the Millennium Development Goals by the 2015 deadline and define a "bold and ambitious" post-2015 development agenda.

He also stressed the importance of delivering a meaningful climate change agreement before the end of next year, adding that the UN Climate Summit on Tuesday "should generate strong political will with bold announcements."

The much-anticipated one-day UN Climate Summit will focus on reducing greenhouse gas emissions, limiting deforestation and mobilizing financial support for action on the climate.

Addressing the opening of the ICPD special session, Sam Kahamba Kutesa, president of UN General Assembly, urged world leaders to commit to stronger action.

"Poverty, discrimination, as well as income and wealth inequality threaten economic growth, the well-being of individuals, societies, and our planet, and are relevant to the discussions at tomorrow's Climate Summit and the general debate that follows," he said.