China should speed up its transition from coal, the new chief US climate negotiator John Podesta said Thursday, while pledging to maintain open dialogue with Beijing.

"China is the largest emitter (of greenhouse gases) in the world... They still have online in my view more coal than they need, and more coal than is good for the health of the world," Podesta said in Tokyo.

Podesta praised the agreement struck by his predecessor John Kerry and his Chinese counterpart Xie Zhenhua in November to deepen climate cooperation, as well as Beijing's role in the UN's COP28 conference in Dubai in December.

"I think keeping... lines of communication open is important so that we can find and produce the kind of result we saw in Dubai, where all the countries of the world agreed to transition away from fossil fuels," Podesta said.

But he added: "We just hope that their (China's) transition away from coal would be a little faster than their current schedule."

The United States is "taking steps to decarbonise our power sector... We are historically the world's largest emitter but we take that responsibility seriously," said the 75-year-old Podesta.

"Now China is by far the world's largest emitter. They need to take their responsibility seriously," he told an event organised by the Sasakawa Peace Foundation (SPF).

He said that it was "important to keep the dialogue going and to try and find common ground", while noting that China was also "the fastest deployer of renewable power in the world".

Podesta also suggested that Japan could accelerate its transition to renewable energies.