U.S. climate envoy John Kerry said on Thursday he expected to speak to his Chinese counterpart Xie Zhenhua soon and called him a "capable advocate" for his country on the issue of global warming.

Xie led the Chinese delegation in global climate negotiations from 2007 to 2018 and was recognized for playing a key role in forging the Paris Agreement.

"I know him very well because I've worked with him for ... 20 years or so," Kerry, former secretary of state, told Reuters in an interview. "He's been a long time ... leader and a believer, we know each other and have respect for, I think, each other's efforts thus far."

Xie, 71, is reported to have served as China's climate envoy until early 2020. Since then, the 71-year-old has remained a special adviser on climate change to the central government and presided over the Institute of Climate Change and Sustainable Development at Tsinghua University.

China has managed to preserve ties with the U.S. on climate issues despite Trump's withdrawal from the Paris Agreement in 2017, Xie said in an interview with Bloomberg as head of Tsinghua University's Institute of Climate Change and Sustainable Development in October.

"In fact, we have never lost contact with state governments, universities and enterprises in the U.S., we have been maintaining effective cooperation," Xie was quoted by Bloomberg as saying. "Regardless of domestic situation in the U.S., we are always willing to carry out cooperation."

The reappointment of the veteran climate negotiator was thought to signal that Beijing is looking to engage the Biden administration on the issue.