Cooperation between China and the United States, the world's biggest economies and top polluters, has been key in the past to breaking deadlocks during negotiations at the annual UN climate talks.

But President Donald Trump, who has pulled the United States out of the Paris climate agreement, and his government have shunned this year's conference in Belem, a city in the Brazilian Amazon.

"Addressing climate change needs every country. We hope that some day, and we also believe that some day in the future, the US will come back," Li Gao, who is also a deputy environment minister, told AFP.

While Trump promotes fossil fuels and rolls back the green tech policies of his predecessor Joe Biden, China is installing more renewable energy sources and putting more electric vehicles on its roads than any other country.

Li said China's priority at COP30 is to support the Brazilian presidency "together with others to send out a very strong political signal that the green low-carbon transition cannot be reversed" and that "international cooperation cannot be reduced."

"It is very important that parties here show political solidarity and commit to work together to address climate change and make sure this COP is an implementation COP," he added.

Li urged countries to "avoid the negative impact of, for example, geopolitical unilateralism or protectionism."

A major issue being discussed at the Conference of the Parties in Belem is how to provide money to help developing countries transition to green energy and adapt to climate change.

The COP29 gathering in Baku last year ended with developed nations agreeing to provide $300 billion annually in climate finance to poorer countries by 2035, a figure criticized as way below what is needed to meet the challenge.

They also set a much less specific target of helping raise $1.3 trillion annually from public and private sources.

A report released by the heads of COP29 and Brazil's COP30 presidency says the world has all the tools to reach the target.

"We welcome the report for the $1.3 trillion, but we think it is crucial that developed countries fulfil the commitment for $300 billion, because it's their responsibility," Li said.