UN climate talks in Glasgow, Scotland, ended on Saturday with a deal that targeted fossil fuels for the first time.

But India, backed by China and other coal-dependent developing nations, rejected a clause calling for a "phase out" of coal-fired power, and the text was changed to "phase down".

"In terms of China and India, they will on this particular issue have to explain themselves," Sharma told a news conference at Downing Street in London on Sunday.

British Prime Minister Boris Johnson said: "Whether the language was 'phase down' or 'phase out' doesn't seem to me as a speaker of English to make that much difference.

"The direction of travel is pretty much the same."

Johnson said COP26 had delivered a mandate to cut the use of coal-powered generation that was backed up by real action from individual counties.

"When you add all that together, it is beyond question that Glasgow has sounded the death knell for coal power," he said at the press conference.

But he said his delight at the progress achieved was tinged by disappointment that the deal did not go further.

"Sadly, that's the nature of diplomacy," he said. "We can lobby, we can cajole, we can encourage, but we cannot force sovereign nations to do what they do not wish to do."

Australian Associated Press