WASHINGTON — The leaders of Russia and China put aside their raw-worded disputes with U.S. President Joe Biden on Thursday long enough to pledge international cooperation on cutting climate-wrecking coal and petroleum emissions in a livestreamed summit showcasing America’s return to the fight against global warming.

Neither Vladimir Putin nor Xi Jinping immediately followed the United States and some of its developed allies in making specific new pledges to reduce damaging fossil fuel pollution during the first day of the two-day U.S.-hosted summit. But climate advocates hoped the high-profile — if glitch-ridden — virtual gathering would kickstart new action by major polluters, paving the way for a November U.N. meeting in Glasgow critical to drastically slowing climate change over the coming decade.

The entire world faces “a moment of peril” but also “a moment of opportunity,” Biden declared, speaking for the virtual summit of 40 world leaders. Participants appeared one after the other onscreen for what appeared to be a mix of live and recorded addresses.

“The signs are unmistakable,” Biden said. “The science is undeniable. The cost of inaction keeps mounting.”

Biden’s new U.S. commitment, timed to the summit, would cut America’s fossil fuel emissions as much as 52% by 2030. It comes after four years of international withdrawal from the issue under President Donald Trump, who pulled the U.S. out of the 2015 Paris climate accord.

Biden’s administration this week is sketching a vision of a prosperous, clean-energy United States where factories churn out cutting-edge batteries and electric cars for export, line workers re-lay an efficient national electrical grid and crews cap abandoned oil and gas rigs and coal mines.

But Senate Republican leader Mitch McConnell dismissed the administration’s plans as costly and ineffective. “This is quite the one-two punch,” McConnell said in a Senate speech Thursday. “Toothless requests of our foreign adversaries ... and maximum pain for American citizens.”

At the summit, Japan announced its own new 46% emissions reduction target and South Korea said it would stop public financing of new coal-fired power plants, potentially an important step toward persuading China to curb building and funding of new ones as well.