More than 20 countries called for the tripling of world nuclear energy capacity at UN climate talks on Saturday as part of efforts to achieve net-zero emissions by 2050.

A declaration endorsed by nations ranging from the United States to Ghana to Japan and several European countries said nuclear energy plays a "key role" in reaching the goal of carbon neutrality.

The use of nuclear energy as a cleaner alternative to fossil fuels is controversial as environmental groups are concerned about safety and the disposal of nuclear waste.

"We are not making the argument to anybody that this is absolutely going to be a sweeping alternative to every other energy source," US climate envoy John Kerry said at the COP28 conference in Dubai.

"But we know because the science and the reality of facts and evidence tell us that you can't get to net zero 2050 without some nuclear," he said.

"These are just scientific realities. No politics involved in this, no ideology involved in this."

The aim is to triple nuclear energy capacity by 2050 from 2020 levels.

The other countries that signed up to the declaration include Britain, Bulgaria, Canada, the Czech Republic, Finland, France, Hungary, South Korea, Moldova, Mongolia, Morocco, the Netherlands, Poland, Romania, Slovakia, Slovenia, Sweden, Ukraine and the United Arab Emirates.

"While we appreciate that the Biden administration is looking to invest in alternatives to fossil fuels, we don't have time to waste on dangerous distractions like nuclear energy," said Jeff Ordower, North America director at environmental group 350.org. (AFP)