President Biden heads to the climate summit in Glasgow aiming to show that the U.S. is ready to take a leadership role on global warming, but with few concrete options for rallying international support for the tough measures scientists say are needed.

The summit, which is sponsored by the United Nations and begins Sunday, provides a stage for world leaders to pledge their national commitments to stem global warming. They are also expected to wrangle over an array of thornier issues, including who should bear the biggest burden...

President Biden heads to the climate summit in Glasgow aiming to show that the U.S. is ready to take a leadership role on global warming, but with few concrete options for rallying international support for the tough measures scientists say are needed.

The summit, which is sponsored by the United Nations and begins Sunday, provides a stage for world leaders to pledge their national commitments to stem global warming. They are also expected to wrangle over an array of thornier issues, including who should bear the biggest burden for cutting emissions.

Mr. Biden has staked a large part of his legacy on U.S. leadership, but he arrives with his plan to spend $555 billion to cut greenhouse gas emissions still awaiting congressional approval and with a key element—a $150 billion program aimed at pushing utilities to draw more power from clean-energy sources—cut under pressure from Sen. Joe Manchin (D., W.Va.).

He now needs international support for what is a global problem, and for that he must overcome skepticism from other nations that the U.S.—after years of waffling on climate policy—can assume the mantle of leadership.

Developing nations want the U.S. and other wealthy nations to fork over more money to help transition to cleaner sources of power. And they believe it is unfair that the U.S. is asking developing countries to sacrifice for the good of the planet after the U.S. spent decades industrializing without any restrictions on its growth.

U.S. Secretary of State Antony Blinken and India's Foreign Minister Subrahmanyam Jaishankar met Saturday at the G-20 summit in Rome.

Photo: Andrea Solaro/Associated Press

India’s Foreign Affairs Minister Subrahmanyam Jaishankar, whose country is the third-largest contributor to greenhouse gas emissions, is among those who say the commitment by the U.S. and other wealthy nations to raise $100 billion a year to help poorer countries to transition to cleaner energy isn’t enough.

“One-hundred-billion dollars is less than the money [that the] NFL is making from media rights,” Mr. Jaishankar said recently.

Former Secretary of State John Kerry, the U.S. special climate envoy, said a new study showing that wealthy nations will meet their $100 billion-a-year climate finance commitment for the first time in 2023 is a sign of progress, even though that is three years later than promised.

He acknowledges that it isn’t enough money in the long run, but that governments alone don’t have the money to raise that total to the trillions of dollars a year ultimately required.

“People are right to worry about why it’s taken so long, but I’m proud of what the United States has done to help pull that money together and to put us on track to produce it,” Mr. Kerry said by telephone from London.

Mr. Kerry said too many countries are refusing to act aggressively enough to meet the goals of the Paris agreement, which set a collective target of limiting the earth’s warming by the end of the century to well under two degrees Celsius compared with the preindustrial era, and to strive to keep warming to 1.5 degrees.

“Yes, there will be a gap in Glasgow,” Mr. Kerry said. “Not every country is going to commit this year to hit the 1.5. But they are committing to do things that [are] beginning to change their approach and economy, and over the next year or so we have time to continue the process of transformation.”

Mr. Kerry and other U.S. officials say their top goal in Glasgow is to keep the momentum going. They note that in the lead-up to the summit more than 140 countries, including major emitters such as Japan and Brazil, have announced more aggressive commitments to reduce their greenhouse gases.

John Kerry, the U.S. special climate envoy, and other U.S. officials say their top goal in Glasgow is to keep the momentum going.

Photo: pool/Reuters

U.S. officials said more successful collaboration at Glasgow can send a signal that governments and businesses should get even more aggressive.

But that type of intangible goal is a political challenge for world leaders looking to soothe public frustration over government inaction, former diplomats said. At Glasgow, also known as COP26, there is no grand bargain on the table for dramatic emissions reductions that world leaders can tout as a breakthrough.

“COP26 was always going to be very difficult,” said Kaveh Guilanpour,

vice president for international strategies at the Center for Climate and Energy Solutions, an environmental group that works with businesses and governments, and a former climate negotiator for small island nations. “Glasgow was never going to be a Paris moment.…COP26 is much more complicated, and it makes it much harder to define what success means.”

Mr. Biden has tried to convince other countries to ramp up their ambition in part by showing a greater financial commitment and more aggressiveness in the U.S. The U.S. has cut its greenhouse gas emissions by about 20% since 2005, thanks to environmental measures and a shift from coal power, but that progress has been leveling off in recent years.

Mr. Biden earlier this year committed to cut U.S. emissions 50%-52% below 2005 levels by 2025. But the U.S. isn’t certain to meet a lower interim target set by former President Barack Obama. And it won’t meet Mr. Biden’s without additional federal action, such as new regulations and the renewable-energy tax credits included in the social-spending and climate legislation currently before Congress, according to outside analysts.

The pending half-a-trillion-dollar plan to reduce U.S. emissions would be the largest in the country’s history, but it is still a framework agreement pending congressional approval.

Money is a sticking point in climate-change negotiations around the world. As economists warn that limiting global warming to 1.5 degrees Celsius will cost many more trillions than anticipated, WSJ looks at how the funds could be spent, and who would pay. Illustration: Preston Jessee/WSJ The Wall Street Journal Interactive Edition

European allies see Mr. Biden as a welcome change from former President Donald Trump, who withdrew the U.S. from the Paris Agreement. But they have taken note of Mr. Biden’s struggles to turn his agenda into law, European officials say.

In China, the world’s No. 1 emitter of greenhouse gases, leaders can mandate climate action and boast of having met past climate pledges to curb the growth of their emissions. This year, they repeatedly drew contrasts with Washington by highlighting the divide between its promises and actions.

Neither China nor the U.S. have enacted policies that will meet the 1.5-degree target, according to Climate Action Tracker, an independent group that analyzes countries’ climate plans. It ranks China’s efforts as “highly insufficient” and U.S. efforts as “insufficient.”

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Policies implemented by the European Union, Japan and Chile were also categorized as insufficient, while the U.K., Costa Rica and Nigeria were labeled “almost sufficient.” Russia and Saudi Arabia were among countries ranked “critically insufficient.”

Some longtime climate advocates have privately started to make comparisons between the Glasgow summit and a December 2009 United Nations meeting in Copenhagen. The Copenhagen summit was Mr. Obama’s first as president, and activists had sky-high expectations about what could be achieved.

In the end, the Copenhagen negotiations themselves produced only incremental progress, prompting frustration from activists, who called it a failure. Like Copenhagen, the Glasgow summit isn’t expected to result in a game-changing agreement.

Some world leaders still harbor anger toward the U.S. for its decision not to ratify the 1997 Kyoto Protocol, the first major global agreement to address climate change, and Mr. Trump’s decision to withdraw from the Paris accord and undo many of Mr. Obama’s climate regulations.

Yvo de Boer, who served as the executive secretary of the U.N. Framework Convention on Climate Change during the Copenhagen summit, said foreign diplomats now better understand the political limits of U.S. presidents.

When asked if world leaders can set aside how the U.S. has changed course on climate change, he said, “For me, it’s a bit like: Are you able to ignore the infidelities of a straying wife?” Despite any misgivings, he said, “the United States is too important to ignore.”

—Georgi Kantchev, Rajesh Roy and Sha Hua contributed to this article.

Write to Timothy Puko at tim.puko@wsj.com and Andrew Restuccia at andrew.restuccia@wsj.com