Rio de Janeiro (AFP) - Western powers and Russia on Tuesday blamed each other for a dramatic escalation in the Ukraine war, 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-emission 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 loosen its rules on using nuclear weapons, amid warnings from Russian Foreign Minister Sergei Lavrov, who was at the G20, 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” while French President Emmanuel Macron expressed concern at “Russia’s bellicose and escalatory declarations.”

Chinese leader Xi Jinping, the most powerful figure at the G20 given Biden’s impending departure from the White House, used the summit to stress that the planet was facing growing “risks and challenges.”

With the clock ticking on the return of an isolationist Trump, the Chinese leader has cast himself as a peacemaker.

His attempts, together with Brazil, to get Russia and Ukraine to the negotiating table have so far been rebuffed by Kyiv.

- ‘Irresponsible rhetoric’ -

A spokesperson for the US National Security Council traveling with Biden condemned Moscow’s nuclear posturing as “more of the same irresponsible rhetoric from Russia, which we have seen for the past two years.”

German Chancellor Olaf Scholz, however, said the heightened stakes illustrated why he is refusing to give Ukraine sophisticated Taurus missiles.

But he added that Russia’s deployment of North Korean troops in the conflict, the apparent trigger for Biden’s U-turn on long-range missiles, was “a further escalation that cannot simply be allowed to happen.”

The summit’s joint declaration on Monday made no mention of Moscow’s aggression in the war, saying only that the leaders welcomed “all relevant and constructive initiatives that support a comprehensive, just, and durable peace” in Ukraine.

The summit statement also had the leaders urging an end to conflict in the Middle East, where Israel is waging offensives in both Gaza and Lebanon.

- Climate talks -

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 touting his progress in weaning the US off fossil fuels in a valedictory tour of South America that took him to Peru and the Amazon rainforest, told his G20 counterparts: “I urge us to keep the faith and keep going.”

“This is the single greatest existential threat to humanity.”