The agreement was reached by US special envoy for climate John Kerry and his Chinese counterpart Xie Zhenhua during two days of talks in Shanghai last week, according to a joint statement.

The two countries "are committed to co-operating with each other and with other countries to tackle the climate crisis, which must be addressed with the seriousness and urgency that it demands," the statement said.

China is the world's biggest carbon emitter, followed by the United States.

The two countries pump out nearly half of the fossil fuel fumes that are warming the planet's atmosphere.

Their co-operation is key to the success of global efforts to curb climate change, but frayed ties over human rights, trade and China's territorial claims to Taiwan and the South China Sea have been threatening to undermine such efforts.

Meeting with reporters in Seoul on Sunday, Kerry said the language in the statement is "strong" and that the two countries agreed on "critical elements on where we have to go".

Noting that China is the world's biggest coal user, Kerry said he and Chinese officials had a lot of discussions on how to accelerate a global energy transition.

"I have never shied away from expressing our views shared by many, many people that it is imperative to reduce coal, everywhere," he said.

President Biden has invited 40 world leaders, including Chinese President Xi Jinping, to the April 22-23 summit.

The US and other countries are expected to announce more ambitious national targets for cutting carbon emissions, along with pledging financial help for climate efforts by less wealthy nations.

It is unclear how much Kerry's China visit would promote US-China cooperation on climate issues.

Chinese Vice Foreign Minister Le Yucheng signalled on Friday that China is unlikely to make any new pledges at next week's summit.

"For a big country with 1.4 billion people, these goals are not easily delivered," Le said.

"Some countries are asking China to achieve the goals earlier. I am afraid this is not very realistic."

Biden, who has said that fighting global warming is among his highest priorities, had the United States rejoin the historic 2015 Paris climate accord in the first hours of his presidency, undoing the US withdrawal ordered by his predecessor Donald Trump.

According to the US-China statement, the two countries would enhance "their respective actions and cooperating in multilateral processes, including the United Nations Framework Convention on Climate Change and the Paris Agreement".

Australian Associated Press