The U.K. will become the first major industrialized nation to end all public finance for fossil fuel projects overseas, in an effort to mark itself out as a leader in tackling climate change.

Prime Minister Boris Johnson will make the announcement at a virtual United Nations summit on Saturday, which he’s co-hosting with France, Italy and Chile. More than 70 world leaders are due to attend the event, alongside Pope Francis and Apple Inc. Chief Executive Tim Cook, who will each pledge to step up ambitions to curb emissions.

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The summit, which has been planned for months, comes as Johnson’s government is locked in fraught negotiations to avoid a chaotic split from the European Union single market on Dec. 31.More fromLofty Climate Goals Get Reality Check at Global SummitXi Disappoints and Activists Slam Baby Steps: Climate UpdateChina’s Xi Takes Small Step to Boost Emission Reduction GoalsMacron Urges G-20, Big Companies to Boost Climate Reporting

He wants to use green policies to prove that the U.K. will continue to have influence outside the EU’s trading bloc, including to bolster relations with U.S. […]