US President Joe Biden said on Sunday that the agreements made at the G20 summit including pledging to limit global warming to 1.5 degrees above Celsius, proved "the power of America showing up".
The world's major economies committed to taking "effective actions" against global warming, and promised action on coal, though Britain and the UN said the Rome talks had not gone nearly far enough.
Biden nonetheless said the leaders made progress with an agreement to end funding for new unabated coal plants abroad, as well as the approval of a global minimum tax on the world's largest companies.
The leaders had made "tangible progress" on key issues, from climate change to the coronavirus pandemic and the economy, ahead of the COP26 climate talks that opened on Sunday in Glasgow.
And he said the successes at the talks were largely down to US diplomacy.
"We got significant support here, significant support. The US of A is the most critical part of this entire agenda, and we did it," he said.
The talks went ahead without the leader of China, the world's largest emitter. President Xi Jinping instead appeared via video link, as did Vladimir Putin of Russia, another major polluting country.
Biden said he was disappointed that Russia and China "basically didn't show up in terms of any commitments to deal with climate change".
"There's a reason why people should be disappointed in that. I found it disappointing myself," he said.
But the US would "continue to focus on what China is not doing, what Russia is not doing, and what Saudi Arabia is not doing", he said.