Global leaders say they want decisive action on tackling climate change at a crunch U.N. summit this year. The behind-the-scenes arguing among Group of Seven delegates — when progress was blocked by last-minute nerves, political tensions and a shortfall of funding — shows just how far they have to go.

Diplomats and ministers working toward the COP26 U.N. climate talks starting in Scotland in October worry that the summit’s chances of success may be in jeopardy. One senior British figure privately said the vital gathering is likely to disappoint.

If leaders cannot step up in Glasgow and agree to measures to keep global warming to 1.5 degrees Celsius, and to deliver on a $100 billion-a-year financing pledge to help the poorest countries adapt, the consequences for the planet could be dire.