LONDON - U.S. climate envoy John Kerry called on countries on Thursday to take a "more critical step" in tackling climate change by stopping any new unabated coal-fired power, just over three months before U.N.-sponsored climate talks begin in Dubai.

Pointedly reminding an audience in Scotland's capital Edinburgh that the United States and China had agreed two years ago there should be no more foreign financing of coal-fired power plants, Kerry said it was time to go further.

"Now is the time for all of us to join together and take a more critical step - there should be no more permitting of any new unabated coal-fired power anywhere in the world. Period," he said, according to a transcript of his speech at an event in Edinburgh.

"Knowing what we know are the impacts and given the alternative options, there is no rational reason for contributing more to the problem by turning to the world's dirtiest fuel burned in the dirtiest way," he said in an address to launch the "Scottish Global Dialogues".

Last month, Kerry said in Beijing it was "imperative that China and the United States make real progress" before the COP28 global climate talks which begin in late November, when China's reliance on coal is likely to be discussed.

China has pledged to start reducing coal consumption, but not until 2026, and new coal power project approvals have accelerated since last year.

Kerry described the increased frequency of extreme weather events, saying today's situation was "one of the most dangerous moments in human history".

To change that, he said, countries must boost financing to new technologies, the fossil fuel industry "must step up" and that politicians should beware of those who "have declared war on facts and science" by denying climate change.

"This is one of the most dangerous moments in human history," he said. "But it may also be the greatest moment of opportunity for human advancement."

(Reporting by Elizabeth Piper; editing by David Evans)