The American actors-turned-environmental campaigners headlined a summit of local leaders from around the world on the sidelines of the UN climate conference, aiming to help inject some much-needed momentum into the talks.

“We didn’t come to Paris to make history: we came to shape the future. This group is uniquely positioned to do exactly that,” said Michael Bloomberg, the co-host of the local leaders’ summit. “We will put local climate action on the global stage. So far, the international negotiations have not recognised the contributions that local leaders can make. We are speaking with one voice, and that voice must be heard.”

But at the venue for the 195-nation talks in Le Bourget on the northern outskirts of Paris, negotiators were entrenched in familiar battle-lines over who should shoulder the cost for the effort to tame climate change.

The planned agreement would establish a universal framework for cutting greenhouse gas emissions that trap the Sun’s heat, warming Earth’s surface and oceans and disrupting its delicate climate system.

Scientists warn Earth will become increasingly hostile for mankind as it warms, such as with rising sea levels that will consume islands and populated coastal areas, as well as catastrophic storms and severe droughts.

However cutting emissions requires a shift away from burning coal, oil and gas for energy, as well the destruction of carbon-storing rainforests — costly exercises that powerful business interests are determined to press on with.

Rich nations have also been reluctant during two decades of UN negotiations to comply with demands from poorer countries that they must pay for the shift to renewable technologies, as well as to cope with climate change.

At stake is hundreds of billions of dollars that would need to start flowing from rich to developing nations from 2020, under the planned Paris pact. But, with time running out before the talks’ scheduled end on December 11, the feuding sides had yet to bridge their differences.