Climate negotiators from the world’s top two greenhouse gas emitters are set to meet this week in Washington for talks on curbing potent planet-warming pollutants, promoting energy efficiency and other issues.

The Wednesday and Thursday sessions will bring together John Podesta, the US senior adviser to the president for international climate policy, and Liu Zhenmin, China’s special envoy for climate change. 

Though the two men have long histories working on climate and environmental issues — and have spoken since their appointments earlier this year — this represents their first formal face-to-face summit before global negotiations in Azerbaijan this November. 

Climate has been a rare issue for collaboration between the two superpowers amid disagreement over trade policy, intellectual property, human rights and the future of Taiwan. The two countries last year laid out a plan for cooperation across key climate topics, including addressing the potent greenhouse gas methane, the circular economy, energy efficiency and the transition away from fossil fuels. 

The State Department said in a news release that this week’s talks under a bilateral working group were “aimed at accelerating concrete climate actions this decade.”

Podesta and Liu face trickier terrain, including debates over the future of international climate finance and intensifying scrutiny of China’s dominant role producing clean technology, such as electric vehicles and solar panels helping fuel the energy transition.

Treasury Secretary Janet Yellen has warned that Chinese excess capacity and record exports of green technology are distorting the global economy. Liu has countered that efforts by the US and European Union to stem China’s dominance risk slowing the fight against climate change. 

In addition to meeting Podesta, Liu, who will be in the US until May 16, will also speak with officials at the United Nations, local governments and think tanks, according to a statement from China’s Ministry of Ecology and Environment.