Ukraine’s allies and Russia on Tuesday traded blame for a dramatic escalation in the war in Europe, which dominated the final day of talks at a G20 summit in Rio de Janeiro. The two-day gathering wrapped up with a plea from Brazilian President Luiz Inacio Lula da Silva for the world’s most powerful leaders to rescue stalled UN climate talks in Azerbaijan, calling it a matter of the planet’s “survival.” Joe Biden, attending his last summit as US president before he hands power to Donald Trump — a noted climate skeptic — also appealed for urgent action. “History is watching us,” he urged. But Biden’s decision to suddenly reverse key US policy on Ukraine in his last weeks in office took away attention from Brazil’s anti-poverty, anti-emissions G20 agenda. On the eve of the gathering, Biden gave Kyiv the green light to use US missiles to strike deep inside Russia for the first time, in apparent response to Moscow enlisting North Korean soldiers to fight in Ukraine. The move prompted the Kremlin to announce it was loosening its rules on using nuclear weapons, causing alarm among Kyiv’s backers in Washington, European capitals and elsewhere. Russian Foreign Minister Sergei Lavrov, who was at the G20, declared that the United States and Russia were “on the brink of direct military conflict.” British Prime Minister Keir Starmer criticized the “irresponsible rhetoric coming from Russia,” sentiments echoed by a spokesperson for the US National Security Council. French President Emmanuel Macron said he had asked Chinese counterpart Xi Jinping to “use all his influence” with Russian leader Vladimir Putin to try to get him to “listen to reason.” Xi, who has cast himself as a defender of the international order at the advent of a new Trump era, held back-to-back meetings with other leaders in Rio. At each turn, the Chinese leader, who was received with greater fanfare than a lame-duck Biden, stressed that the world was facing a new period of “turbulence.” China and Brazil this summer unveiled a plan to get Russia and Ukraine back to the negotiating table, but were rebuffed by Kyiv because Moscow was not required to pull back first. The summit’s joint declaration made no mention of Russian aggression, saying only that the leaders welcomed “all relevant and constructive initiatives that support a comprehensive, just, and durable peace” in Ukraine. President Lula used his summit hosting duties to rally support for a global campaign against hunger and try to spur on the stalled COP29 climate talks in Azerbaijan’s capital Baku. “We cannot leave the task of Baku until Belem,” Lula said Tuesday, referring to the Amazonian city that will host next year’s UN climate talks. But a G20 statement on the matter fell short of the shot in the arm sought by climate negotiators gathered in Azerbaijan. While acknowledging the need for trillions of dollars in climate finance for poorer nations, the leaders failed to explicitly mention the need to transition away from fossil fuels. Lula said that next year’s conference would be the “last chance” to avoid “irreversible” damage wrought by Earth’s warming. Biden, who has been using a valedictory tour of South America to tout his climate legacy, told his G20 counterparts: “I urge us to keep the faith and keep going.” “This is the single greatest existential threat to humanity.” But in a symbol of the elderly leader’s imminent disappearance from the global stage, he missed out on the summit’s first group photo, his absence going unnoted by his peers. Another photo was taken Tuesday that Biden featured in. Lula, who handed over the G20 presidency to fellow Global South advocate South Africa, came away with wins on two pet projects. The left-winger who grew up in poverty, got the leaders of 80 countries, including a reluctant Argentine President Javier Milei, to join an alliance to end world hunger. And G20 members, at his urging, also agreed to cooperate to get the world’s billionaires to pay more in tax, a key demand of anti-poverty campaigners.