UN Secretary-General Ban Ki-moon met with President Xi Jinping's special envoy on Thursday on the eve of the Paris Agreement signing ceremony and acknowledged China's contribution to the climate breakthrough.

"China played such an important role in making it possible," said Ban. "China has been pushing for energy conservation and emission reduction and promoting South-South cooperation. The country shows its leadership in tackling climate change."

Xi's special envoy, Vice-Premier Zhang Gaoli, applauded the historical significance of the Paris Agreement and the effort of the United Nations and Secretary-General Ban.

High-level officials from nearly 160 countries - including US Secretary of State John Kerry - will sign the agreement at UN headquarters in New York on Friday, which is also International Mother Earth Day.

"We believe the signing ceremony will further bring the Paris deal into force," said Zhang. "And China will continue to participate actively in global collaboration to combat climate change and to keep promoting South-South cooperation."

Zhang said China, as the largest developing country, recognizes its responsibility, and the country will adhere to a path of innovative, coordinated, green, open and shared development.

China also will build more low-carbon cities, push for zero carbon projects and create a nationwide carbon market, Zhang said.

Ban said the UN wishes to increase cooperation with China and together implement the agreement.

"China will uphold the purposes and principles of the UN Charter and deepen China's relationship with the UN," Zhang said.

After the signing ceremony, China will begin the legal process to join the agreement and will ratify it as soon as possible, said Su Wei, director of the Department of Climate Change of the National Development and Reform Commission.

Countries that don't sign the agreement on Friday still will have a year to do so. Those that sign then must have the agreement ratified by their own legislative bodies.

At least 55 countries, representing at least 55 percent of global greenhouse gas emissions, must ratify the agreement before it can take effect. China and the United States account for 38 percent of the world's greenhouse gas emissions.

The agreement aims to hold the increase in the global average temperature to less than 2 degrees Celsius above pre-industrial levels and to work toward limiting the increase to 1.5 C.

International environmental groups are praising China for significantly increasing the chances that the agreement can take effect before the 2020 deadline.

"These signals significantly increase the chance that the agreement will enter into force this year," said Jake Schmidt, director of the International Program at the Natural Resources Defense Council, which is based in New York.

Eliza Northrop, a researcher at the World Resources Institute, also said the signing by China and the US will give a major boost to efforts to reach the threshold for entry into force.

"It is reasonable to think the entry into force would happen in 2017," she said. "But given the varying timelines for countries to complete their domestic approval processes, the timing of entry into force is uncertain."

Samantha Smith, leader of the World Wildlife Fund, said more efforts are urgently needed for the climate change meeting next month in Bonn, Germany, to pick up on issues where the Paris meeting left off.

Contact the writers at hezijiang@chinadailyusa.com and zhengjinran@chinadaily.com.cn.