WASHINGTON (AP) — President Joe Biden will open a global climate summit 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 China and other big polluters to speed up efforts of their own.

Biden is offering Americans and the world 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.

His commitment to cut U.S. fossil fuel emissions up to 52% by 2030 will come 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 President Donald Trump. Japan, a heavy user of coal, announced its own new 46% emissions reduction target Thursday before the summit opened, as the U.S. and its allies sought to create momentum.

The Biden administration's pledge would require 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.

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.”

But Biden administration officials, in previewing the new target, disclosed aspirations and vignettes 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 and Vice President Kamala Harris were scheduled to open 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.

Due to the coronavirus pandemic, the summit will play out as a climate telethon-style livestream, limiting opportunities for spontaneous interaction and negotiation.

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 (1.5 degrees Celsius), the Biden administration said.

Biden, a Democrat, campaigned partly on a pledge to confront climate change. He has sketched out some elements 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.

His administration insists the transformation will mean millions of well-paying jobs. Republicans say the effort will throw oil, gas and coal workers off the job. They call his infrastructure proposal too costly.

“The summit is not necessarily about everyone else bringing something new to the table — it’s really about the U.S. bringing their target to the world,” said Joanna Lewis, an expert in China energy and environment at Georgetown University.

It’s an urgent but hardly perfect time for the U.S. to try to spur action.

The world's top two climate offenders, China and the United States, are feuding over non-climate 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 earlier this month, after a visit from Biden climate envoy John Kerry.

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

And at home, political divisions exposed by Trump's presidency have left the United States weaker than it was at the 2015 Paris accord. Unable to guarantee that a different president in 2024 won't undo Biden's climate work, the Biden administration has argued that market forces — with a boost to get started — will soon make cleaner fuels and energy efficiency too cheap and consumer-friendly to trash.

Having the United States, with its influence and status, back in the climate game is important, said Lauri Myllyvirta, lead analyst at the Centre for Research on Energy and Clean Air in Helsinki.

But hoping the world will forget about the last four years seems like wishful thinking, he said.

“There is too much of an impulse in the U.S. to just wish away Trump’s legacy and the fact that every election is now basically a coin toss between complete climate denial and whatever actions the Democrats can bring to the table,” he said.

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Knickmeyer reported from Oklahoma City. Associated Press writers Ashok Sharma in New Delhi, Joe McDonald in Beijing, Vladimir Isachenkov in Moscow and Seth Borenstein, Matthew Daly, Alexandra Jaffe and Aamer Madhani in Washington contributed to this report.