China and the United States, the world's two largest emitters of greenhouse gases, are increasing their cooperation in fighting climate change.

US Special Envoy for Climate Change Todd Stern said the US has a very good relationship with China regarding the issue.

"I have worked very closely with my colleague and at this point very good friend Vice-Chairman Xie (Zhenhua) from the NDRC (National Development and Reform Commission)," Stern told a press conference on Friday in Washington.

"We meet all the time and I think we have a very good understanding," Stern said, citing the cooperation with China as a demonstration of US leadership on climate change in the international front.

The two countries set up the China-US Working Group on Climate Change in April during Secretary of State John Kerry's visit to China.

During last June's meeting in Sunnylands, California, Chinese President Xi Jinping and US President Barack Obama agreed that the two countries would work together and with other countries to use the expertise and institutions of the Montreal Protocol to reduce the consumption and production of hydrofluorocarbons (HFCs), a potent greenhouse gas. The move was widely applauded by environmental groups.

During the 5th Strategic and Economic Dialogue in July in Washington, the two countries agreed to five new action initiatives aimed at reducing greenhouse gas emissions and air pollution by tackling the largest sources of emissions in both nations.

These include: reducing emissions from heavy-duty vehicles; increasing carbon capture, utilization and storage (CCUS); increasing energy efficiency in buildings, industry and transport; improving greenhouse gas data collection and management; and promoting smart grids.

"I think that the cooperation between the US and China is increasing all the time," said Stern, who flew to Warsaw, Poland, over the weekend, for the 19th session of the Conference of the Parties (COP-19) of the United Nations Framework Convention on Climate Change, to be held Nov 11 to 22.

According to Stern, teams from the two countries are working on implementation measures for the five initiatives. "So we mean to make progress with respect to the work that we're doing in all of those areas," he said.

There was a considerable amount of cooperation going on between the US Environmental Protection Agency and China's Ministry of Environmental Protection, he said, as well as between the US Department of Energy and China's National Energy Administration.

He described the US heads of the EPA, Gina McCarthy, and DOE, Ernie Moniz, who visited China in late October, as real leaders on the climate change issue.

"They have a broad portfolio, but they're very focused on climate change," Stern said, "and very much engaged with China as well.

"We are eager for a deepening relationship with China on all these issues. After all, we are the two largest emitters," Stern said.

Stern admitted that it was extremely difficult at the moment to get action out of the US Congress on climate change, but he said Obama and Kerry have a strong commitment and Obama announced several ambitious measures using existing regulations, including the reduction of power plant emissions using provisions of the Clean Air Act.

Stern said that the climate change agreement being worked out at the UN meetings will be sensitive to differences and capabilities of different countries.

Xie Zhenhua of China's NDRC, told reporters recently that the key of COP-19 is to implement all the commitments already made.

But since participating nations aim to work out a new agreement by the end of 2015, the Warsaw conference will mostly be to lay a solid foundation for the essential negotiations in 2014 and the final conclusion of a new agreement in 2015, according to Xie.

Contact the writer at chenweihua@chinadailyusa.com