UNITED NATIONS -- UN member states should strengthen efforts to bring the Paris Agreement on climate change into force by the end of the year in order to build a world of sustainable growth, UN Secretary-General Ban Ki-moon said Tuesday.

"With the Paris Agreement on climate change, we are tackling the defining challenge of our time," the secretary-general said at the opening of the General Debate of the UN General Assembly, a week-long annual high-level event at UN headquarters in New York.

"We have no time to lose," Ban said. "I urge you, leaders, to bring the Paris Agreement into force before the end of this year."

"We need just 26 countries more, representing just 15 percent of greenhouse gas emissions," he said.

"I ask you to help lead us to a world of low-carbon growth, increased resilience and greater opportunity and well-being for our children," he added.

The Paris Agreement, adopted in December 2015, needs 55 nations that together account for 55 percent of global greenhouse gas emissions to ratify before it can enter into force.

On Sept. 3, the National People's Congress, China's top legislature, ratified the agreement, a significant international legal document that outlines post-2020 global climate governance.

The much-anticipated Paris Agreement is the third document to attempt to address climate change, following the 1992 United Nations Framework Convention on Climate Change and the 1997 Kyoto Protocol.