"The spotlight is naturally on the G20. They account for 80 percent of global emissions," U.N. Secretary General Antonio Guterres told reporters in Rio de Janeiro. He expressed concern about the state of the COP29 talks in Baku and called on G20 leaders to do more to fight climate change.

Diplomatic tensions over global warming will take center stage at the G20 summit in Brazil this week, as negotiators at U.N. talks in Azerbaijan hit an impasse on climate finance that they hope leaders of the world's 20 major economies can break.

With leaders from the world's biggest economies converging on Rio de Janeiro for a two-day G20 summit starting Monday, the usually relaxed seaside city is under a tight security blanket.Many locals were planning to leave the city of six million during the summit.