UK Prime Minister Boris Johnson urged leaders of the world’s major economies including the United States to deliver on their commitments towards a $100 billion per year climate fund with less than six weeks to go before a UN climate summit.

Johnson and UN secretary-general António Guterres hosted a roundtable of world leaders on Monday to address major gaps on emissions targets and climate finance.

“Too many major economies – some represented here today, some absent – are lagging too far behind,” Johnson said. “I’ll stress that again – for this to be a success we need developed countries to find that $100 billion.”

The closed-door meeting during the annual high-level week of the UN General Assembly includes leaders and representatives from a few dozen countries representing industrialised nations, emerging economies and vulnerable developing countries, said Selwin Hart, assistant secretary-general and special adviser to Guterres on climate action.

Johnson told reporters that he is hopeful the US can deliver on a promise to step up its share of money towards the $100 billion annual goal but “we’ve been here before” and “we’re not counting our chickens”.

US climate envoy John Kerry, who represented the United States at Monday’s meeting, said Washington would deliver more climate aid ahead of the October 31-November 12 COP26 Climate Change Conference in Glasgow, Scotland.

“The United States is crucially important,” Johnson said. “It will send a massively powerful signal to the world.”

“The alarm bell needs to be rung,” he told reporters last week. “Countries are not on target, really, to bridge these gaps in mitigation, finance and adaptation.”

“Will the developed world finally materialise the $100 billion of annual support to developing countries?” Guterres told reporters. “We are not yet there,” he added. “But today there were encouraging declarations in this regard.”