DUBAI: U.N. climate chief Simon Stiell told countries on Wednesday to agree ambitious action to tackle global warming at the COP28 climate summit rather than fall into the trap of point scoring and "lowest common denominator politics".

At a summit where tension is growing over different visions for the future of fossil fuels, Stiell told a news conference: "All governments must give their negotiators clear marching orders. We need highest ambition, not point scoring or lowest common denominator politics."

Stiell's remarks come as the two-week conference approaches its midpoint, which is the time when the opening flurry of announcements and pledges has died down and attention turns to what progress the behind-the-scenes talks have been making.

"We have a starting text on the table ... but it's a grab bag of wish lists and heavy on posturing. The key now is to sort the wheat from the chaff," he said.

"There are many options that are on the table right now which speak to the phasing out of fossil fuels. It is for parties to unpick that, but come up with a very clear statement that signals the terminal decline of the fossil fuel era as we know it."