WASHINGTON (NewsNation Now) —  President Joe Biden opened a global climate summit Thursday with a pledge to cut at least in half the climate-wrecking coal and petroleum fumes that the U.S. pumps out, a commitment he hopes will spur big polluters to speed up efforts of their own.

Biden committed to cutting U.S. fossil fuel emissions up to 52% by 2030 — similar to pledges from allies — at the launch Thursday of an all-virtual climate summit for 40 world leaders, marking a return by the U.S. to global climate efforts after four years of withdrawal under former President Donald Trump.

The Biden administration’s pledge requires by far the most ambitious U.S. climate effort ever undertaken, nearly doubling the reductions that the Obama administration had committed to in the landmark 2015 Paris climate accord.

“Meeting this moment is about more than preserving our planet,” Biden declared, speaking from a TV-style set for a virtual summit of 40 world leaders. “It’s about providing a better future for all of us,” he said, calling it “a moment of peril but a moment of opportunity.”

“The signs are unmistakable. the science is undeniable. the cost of inaction keeps mounting,” he added.”

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

“No nation can solve this crisis on its own, and this summit is a step on a path to a secure, prosperous, and sustainable future,” Biden said in a tweet minutes before the summit began.

The new urgency comes as scientists say that climate change caused by coal plants, car engines and other fossil fuel use is already worsening droughts, floods, hurricanes, wildfires and other disasters and that humans are running out of time to stave off most catastrophic extremes of global warming.

“The United States is not waiting, the costs of delay are too great, and our nation is resolved to act now,” the Biden administration said in a statement. “Climate change poses an existential threat, but responding to this threat offers an opportunity to support good-paying, union jobs, strengthen America’s working communities, protect public health, and advance environmental justice.”

Biden administration officials, in previewing the new target, disclosed aspirations rather than specific plans, budget lines or legislative proposals for getting there. Administration officials briefing reporters in advance of Biden’s announcement made no direct mention of politically tricky moves to wean the U.S. from oil, natural gas and coal. They emphasized the role of technology, including carbon capture and hydrogen power, which have yet to be affordably developed to scale.

Biden previously signed executive actions in January addressing aspects of climate change from pausing new oil and gas leases on federal land to cutting fossil fuel subsidies.

Biden and Vice President Kamala Harris opened the Earth Day summit from the White House East Room before world leaders, including the heads of China, Russia, India, Gulf oil states, European and Asian allies and island and coastal nations already struggling against the effects of climate change. Pope Francis will also take part.

Biden planned to join a second session of the livestreamed summit later in the morning on financing poorer countries’ efforts to remake and protect their economies against global warming.

This is an urgent but hardly perfect time for the U.S. to try to spur action for multiple reasons, and the summit will play out as a climate telethon-style livestream because of the coronavirus pandemic.

World leaders aim to limit global warming to 1.5 degrees Celsius above pre-industrial levels, a threshold scientists say can prevent the worst impacts of climate change.

With the pledge from the United States and other emissions-cutting announcements from Japan, Canada, the European Union and the United Kingdom, countries representing more than half the world’s economy will have now committed to cutting fossil fuel fumes enough to keep the earth’s climate from warming, disastrously, more than 2.7 degrees Fahrenheit, the Biden administration said.

The world’s top two climate offenders, China and the United States, are feuding over nonclimate issues. Chinese President Xi Jinping waited until Wednesday to confirm he would even take part.

India, the world’s third-biggest emitter of fossil fuel fumes, is pressing the United States and other wealthier nations to come through on billions of dollars they’ve promised to help poorer nations build alternatives to coal plants and energy-sucking power grids.

“Where is this money? There is no money in sight,” Environment Minister Prakash Javadekar said ahead of the summit this month, after Biden climate envoy John Kerry visited.

Russian President Vladimir Putin, whose nation by some assessments is the world’s fourth-worst climate polluter, also accepted the U.S. invitation but tension exists over Biden calling him a “killer,” as part of high tensions over Putin’s aggressiveness abroad and U.S. sanctions.

Biden sketched out some of his $2 trillion approach for transforming U.S. transportation systems and electrical grids in his campaign climate plan and in his infrastructure proposals for Congress. But there’s no hard and fast plan detailing how the U.S. will fulfill Biden’s promise to eliminate all carbon emissions from its economy by 2050.

China and the United States together account for nearly half of the world’s climate emissions. Climate experts hope Xi will watch what the U.S. and China’s neighbors pledge and toughen its own emissions goals in following months.

Xi’s government continues building and financing new coal-fired power plants, and China’s emissions are still rising. Myllyvirta, the climate expert at the Helsinki center, said Xi’s comments at recent domestic political forums make clear he is serious about cutting emissions.

Amid U.S. and China disputes over territorial claims, trade practices and human rights, however, the two countries’ presummit pronouncements were an island of climate cooperation in a sea of complaints and grievances. “The international community knows very well who is taking actions, who is playing lip service, who is making contributions and who is seeking one’s own interest,” Chinese Foreign Ministry spokesperson Wang Wenbin said before the summit.

Reporting by Ellen Knickmeyer and Christina Larson. The Associated Press and Reuters contributed to this report.