The US and China have started unofficial conversations on climate-related issues during the COP27 summit in Egypt, a potential signal that relations between the two world superpowers are warming despite a formal suspension of bilateral negotiations on related matters earlier this year.

China’s climate envoy Xie Zhenhua told Bloomberg News on Wednesday that he met with his US counterpart John Kerry for unofficial talks, emphasizing the door is always open on the Chinese side for a joint effort to promote COP27 agenda items at the annual global climate meeting.

“Even as the two countries haven’t resumed official climate talks, we met already for unofficial consultations for a successful COP27,” Xie said before a press briefing in the coastal city of Sharm el-Sheikh in Egypt. 

Kerry said he spoke with Xie at an event sponsored by The Wall Street Journal on Tuesday. Formal talks, however, are not in the cards at this moment, he said. Kerry has repeatedly stressed that the existential threat of climate change is not a bilateral issue.

Both men are interested in resuming talks on curbing methane, combating deforestation and accelerating the green transition, according to people familiar with the matter who asked not to be named because of the sensitivity of the discussions. Kerry has previously described sending unanswered texts and e-mails to Xie in hopes of restarting talks.

Xie said he and Kerry communicated in eight e-mails during the suspension of talks between the two countries as they have been keeping private contact following a friendship of 25 years. The resumption of the private, friendly talks between the two countries was initiated by Xie, he said.

Beijing announced it was halting negotiations with the US over climate and several other issues in August, after US House Speaker Nancy Pelosi visited Taiwan, the self-governing island over which China claims sovereignty.

The freeze had implications for broader, multilateral climate negotiations at the COP27 summit in Sharm el-Sheikh. Collaboration between the two countries in 2014 helped provide the foundation for the Paris Agreement a year later. And a joint declaration in the final days of the COP26 summit in Glasgow last year helped pave the way for a final accord.

Chinese President Xi Jinping is not attending COP27 as he stays in China for internal affairs, hosting visits from overseas leaders, Xie said. Both Xi and President Joe Biden have confirmed they will be at the Group of 20 meetings in Indonesia next week, Indonesian President Joko Widodo said, though Xi’s attendance hasn’t been confirmed by China’s foreign affairs ministry.