Former US senator and secretary of state John Kerry will leave his post as President Joe Biden's special climate envoy after three years but will help Biden's re-election campaign, two administration sources said on Saturday.

The decision by Kerry, 80, 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.

He informed his staff on Saturday about his decision after speaking with Biden on Wednesday, one of the sources familiar with the situation told Reuters, speaking on condition of anonymity. The administration has made no decisions about who may be selected to replace Kerry, the source said.

The sources said Kerry would leave the position later this winter.

Kerry, as secretary of state under Democratic former President Barack Obama, also helped broker the 2015 Paris climate agreement in which nations committed to steps to combat climate change. Kerry previously served as a Democratic senator from Massachusetts and was his party's 2004 presidential nominee, losing to Republican incumbent George W. Bush.

Axios first reported Kerry's plans.

Kerry, a long-time advocate on climate issues, was among the first senior officials who Biden, a Democrat, appointed after winning the 2020 presidential election. Biden, seeking re-election in November, tasked Kerry with restoring American engagement in international climate negotiations after Republican former President Donald Trump withdrew the United States from the Paris agreement.

Kerry, whose appointment as special envoy on climate change did not require US Senate confirmation, has a seat on the National Security Council in the White House, marking the first time an official on that body was dedicated to the climate issue.

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.

Kerry and his Chinese counterpart Xie Zhenhua were instrumental in getting nearly 200 countries to agree to the Paris agreement and UAE Consensus through bilateral agreements they reached. The two worked through some of the thornier issues such as whether developing countries should be responsible for reducing emissions and how countries should commit to moving away from fossil fuel use.

China on Friday announced it had named Liu Zhenmin, a former vice foreign minister, as its new special envoy for climate change after Xie, 74, stepped down due to health reasons.