The United Kingdom, Canada, France, Germany and major coal producer Australia were among the list of mainly wealthy developed economies to sign the voluntary pledge in Azerbaijan.

It commits nations to submit national climate plans early next year that reflect no new unabated coal in their energy systems.

Unabated refers to coal burned without any measures to reduce its emissions, such as carbon capture and storage, technologies criticised as unproven at a large scale.

The pledge does not compel nations to stop mining or exporting coal, which produces more planet-heating carbon emissions than oil and gas, and is a major driver of climate change.

Many of the world's biggest coal-power generators -- including China, India and the United States -- did not sign the "call to action" launched in Baku.

EU climate envoy Wopke Hoekstra, who signed the initiative, said coal power was still growing despite a historic commitment made at last year's COP to use less fossil fuels for energy.

"The commitment to 'transition away from fossil fuels' needs to turn into real steps on the ground," Hoekstra said.

Britain recently became the first of the Group of Seven industrial nations to end all reliance on coal in its power generation.

UK Energy Secretary Ed Miliband said that coal "poses one of the biggest threats" to capping global warming at levels scientists say would prevent the worst consequences of climate change.

This pledge "sends a clear signal from countries around the world that new coal needs to end" by the next COP summit in Brazil, he added.

The inclusion of Australia, a major coal user and exporter, was welcomed by activists at COP29 where raising money for poorer countries has been a bigger priority than efforts to cut heat-trapping emissions.

"This has closed the door on coal. Now we need to lock it," Erin Ryan from Climate Action Network Australia told AFP in Baku.

"It's beyond time that we left it in the past, both in our energy systems and our export markets."

Developing countries including Angola, Uganda and Ethiopia were also among the countries to sign the pledge, which was developed in collaboration with the Powering Past Coal Alliance.