President Joe Biden’s special climate envoy John Kerry has decided to leave his position after three years to help Biden’s re-election campaign, two administration sources said on Saturday.

The decision by the former United States senator and secretary of state comes a month after he played an instrumental in helping broker an international agreement announced in Dubai for nations around the world to transition away from fossil fuels.

The 80-year-old Democrat informed Biden of his intentions to leave on Wednesday, and his staff learned of the decision on Saturday, those officials said.

While the sources said that Kerry would be leaving his position later this winter, they revealed that the administration has not decided who may be selected to replace him.

Kerry’s plans were first reported by Axios.

The long-time climate advocate was appointed by Biden after winning the 2020 election and was tasked with restoring American engagement in international climate negotiations after Donald Trump withdrew the US from the Paris Agreement.

Kerry’s appointment as special envoy on climate change did not require Senate confirmation and he holds a seat on the National Security Council, marking the first time an official on that body is dedicated to climate issues.

In an interview with Reuters in December after COP28, Kerry said he had not made up his mind about his future but said no matter what, he would not take his eyes off of climate advocacy.

“I will continue as long as God gives me the breath and work on it one way or the other,” Kerry said of climate advocacy.

Among Kerry’s top priorities as Biden’s special envoy had been to maintain close diplomatic ties with China on climate change, even as numerous other political and trade tensions simmered.