GLASGOW — In the sprawling encampment that has housed the United Nations climate talks over the past two weeks, delegates from around the world have praised the United States and condemned the United States, but one thing they could not do was ignore the United States.

The Americans, including 13 Cabinet members, seemed to be everywhere at the conference: speaking on public panels, disappearing into windowless rooms, and huddling in hallways and hotel bars to shape the outcome of the talks to protect the planet, along with U.S. interests.

“We believe that this is existential,” said U.S. climate envoy John F. Kerry on Friday in a passionate speech on the floor of a plenary meeting. “And for many of you it’s existential today. People are dying. Today,” Kerry said. “All around the world, the impacts are being felt. Today.”

Throughout the closing debates on Saturday, Kerry worked the massive room, his 6-foot-4 figure easy to spot towering over other delegates.

A year ago, the United States formally withdrew from the climate accord. President Donald Trump had mocked the deal as pleasing Paris rather than Pittsburgh. Biden signed an executive order the first day of his presidency to rejoin. Now the United States is once again, if not indispensable, at least critical, given its diplomatic muscle, financial power and responsibility for its outsize role in contributing to global greenhouse gas emissions that account for 13 percent of the annual total, second only to China.

While climate talks largely stalled under Trump, Kerry’s approach to climate diplomacy put the United States at the forefront of galvanizing international action, even as Biden’s climate agenda remains stalled in Congress. “President Biden made an unprecedented commitment to this,” Kerry said Saturday after the climate deal was signed. Biden attended last week, making announcements on methane and deforestation.

“The United States took this seriously, as we should, after the previous administration was absent during their time in the White House,” Kerry said Saturday. He acknowledged the young people who protested at the global climate summit, saying that they “don’t want this place just to be a place of words. It has to be in the next hours a place of action.”

During the conference here, the United States and European Union have corralled more than 100 countries into supporting deep cuts in emissions of methane, the potent greenhouse gas. The United States has taken part in a coalition to fight deforestation, which is destroying the world’s carbon sinks. The U.S. delegation has also helped convince other nations to halt financing for the construction of foreign coal plants, a pact that includes Japan, South Korea and China, all major funders of such projects.

“In terms of U.S. leadership, it’s important to remember that a lot of what will be counted as COP26 accomplishments are due to the work not of the past 10 days but the past 10 months since Biden took office,” said Pete Ogden, who served at the White House and State Department and is now vice president for climate at the United Nations Foundation.

There are limits to how effectively the United States can lead, given the political realities at home. The U.S. delegation came under fire from other countries who wanted an unequivocal commitment to end all fossil fuel subsidies, but the United States ultimately agreed to end assistance to “unabated” coal and “inefficient” fossil fuel subsidies. “We have some of those subsidies,” Kerry said, adding that the $2.5 trillion that went into subsidies worldwide in recent years is the “definition of insanity.”

The Americans also said privately that signing such a deal would have strained relations with lawmakers like Sen. Joe Manchin III (D-W.V.), the deciding vote for passing the Build Back Better legislation in the Senate. That bill would provide $550 billion to address climate change, largely in the form of tax credits to ease the economic transition to electric vehicles, renewable energy and more efficient buildings and industry.

Bas Eickhout, a Dutch Green Party lawmaker who is in the European Parliament, said he believes that Democrats in Congress want to sharply increase U.S. funding for international climate assistance, but they don’t have the votes to do it. “They acknowledged there was a money problem,” he said, referring to talks he says he’s had with Democrats.

“Unfortunately, the U.S. leadership on climate change continues to be constrained by the limits of what a Democratic administration can do in the face of ongoing GOP opposition,” said Jules Kortenhorst, the chief executive of RMI, a nonprofit focused on renewable energy.

Many negotiators from poorer countries said that they were tired of waiting for a change in U.S. policy when climate change keeps growing more dire all the time. “Small islands cannot always be the ones who are asked to compromise our interests with the objective of reaching consensus,” said Milagros De Camps, the deputy minister for the Dominican Republic and also a representative from the Alliance of Small Island States. “These are not just words that we are conceding, it’s our futures.”

The most difficult issues for the United States, as the richest country in the world, revolved around money. The United States failed to make its portion of the $100 billion payment wealthy countries had promised to deliver in 2020. Some developing countries wanted those funds to be owed to them. Instead, the wealthy countries will hit the $100 billion mark in 2023. By 2025, they plan to have made up for their initial shortfall.

The $11.4 billion Biden promised to devote to climate change three years from now — assuming he gets what he wants from Congress — will only amount to half as much as the E.U. contribution. The population of the United States is three-fourths that of the European Union.

The United States has also avoided earmarking money for “losses and damages” accumulated from harmful emissions since the start of the industrial era. Some poorer countries wanted that money to go into a separate fund. The U.S. delegation worried that it sounded too much like reparations, and they fretted how the money would be managed. But a hedged reference to losses and damages remained in the text, and Kerry was flexible about growing the size of the adaptation funds. Adaptation helps countries cope with the impacts of climate change.

Some of the harshest criticism came from fellow Americans operating on the margins here. Ramon Cruz, the president of the Sierra Club, said on Thursday that the United States “is not negotiating with the best interests of the most vulnerable and in the global community.”

Cruz compared the global negotiations with environmental justice efforts in the United States, where activists are encouraging the government to reinvest in the communities most affected by unjust historic policies. “We would like to see that level of commitment when it comes to adaptation and loss and damage,” Cruz said. If the administration wants to recapture U.S. leadership, “it cannot be just with words, but with actions.”

Kerry has been a linchpin of the U.S. climate team. A former senator, presidential candidate and secretary of state, he has surrounded himself with an experienced team. Younger delegates from other countries have scolded older ones for not understanding the urgency of doing something about climate change, but Kerry largely escaped that lashing.

“Senator Kerry, you could see the passion with him,” said the Pakistani climate envoy Malik Amin Aslam. Saturday afternoon, Kerry could be seen huddling with delegates from developing nations, his expression serious, glasses at the tip of his nose, listening intently in the talks.

Gabonese environment minister Lee White said African nations had been pushing for a carbon markets provision that would set aside a small portion of profits for adaptation projects in the developing world. But the United States and other wealthy countries would not budge on the issue.

“John F. Kerry, I said to him, if we can’t make a contract, if we can’t finalize this in the agreement we’re signing here, is that a moral engagement that you’re willing to take?” White asked. Kerry assured White: He would make a moral commitment. He would give his word. “Now we have to make that happen,” White said. “That was as good as we could do here.”

Kerry and the top E.U. climate official, Frans Timmermans, worked in tight coordination with each other as they held one meeting after another to try to win an agreement, splitting up countries to leverage their influence. The Americans took Brazil and Saudi Arabia, as the European Union worked harder on African countries its members once colonized.

“Having the U.S. back has really helped,” said one European negotiator, speaking on condition of anonymity to discuss the private talks. “Because the U.S. has sway in parts of the world that we don’t.”

One of those places is China, whose chief climate negotiator Xie Zhenhua was brought out of retirement to explore a deal with Kerry. No relationship ranks as important as that of the United States and China, but it has been marred by tensions over trade, as well as Beijing’s policy toward Uyghur Muslims, which the Biden administration has called a “genocide,” and its crackdown on the democracy movement in Hong Kong.

Leading up to the conference, Kerry and Xie had mostly virtual contacts, but there was a meeting in Shanghai during which the two delegations were not allowed to eat together because of pandemic protocols. After staying on the edges in Glasgow, Xie swept unannounced into a media briefing room just before Kerry was to scheduled to speak. The two sides announced a joint working group, promising “enhanced climate action” to stay within the temperature limits laid down in the Paris accord.

Later, on the conference’s final day, Xie and Kerry shuttled back and forth across the room to iron out a deal. China and India insisted on changing the “phase-out” of coal to “phase-down,” a setback for most countries who had agreed to brush their domestic concerns aside.

Italian Ecological Transition Minister Roberto Cingolani said he could appreciate the subtleties of achieving progress on global warming. When Italy hosted the Group of 20 summit earlier this year, he had shepherded climate talks and was charged with forging a compromise between the United States, China and other major economies.

“I know that there is a world situation, but there is also your local situation, and you have to find a balance. I don’t even want to think how difficult this is in the United States,” Cingolani said. “The United States are back. We were missing you in the global fight for a while.”

Sarah Kaplan and Brady Dennis contributed to this report.