“When I looked at that, I said, ‘We cannot do this and we will not do this,’” Secretary of State John Kerry told reporters afterward. “‘And either it changes or President Obama and the United States will not be able to support this agreement.’”

And so the scrambling began. With the clock ticking and the start of the talks’ final meeting already delayed by several hours, top U.S. negotiators huddled in a cavernous plenary hall in this suburb of Paris trying to get the language changed. At the same time, supporters of the deal feared that re-opening the text would lead to a flood of revisions from other countries, possibly swamping the entire effort.

In the end, the U.S. persuaded the summit’s French hosts to change the wording, and the tweak was read aloud by a delegate in the plenary hall, lost in a package of other technical revisions. Minutes later, French Foreign Minister Laurent Fabius banged his gavel and the most significant international climate change deal in history won the resounding approval of 196 governments, representing nearly every country on the planet.

The 11th-hour kerfuffle capped an often-torturous 13 days of negotiations that stretched through the night and into the early morning almost every day this week. This year’s talks weren’t marked by the sharp-toothed bickering that has defined two decades of climate negotiations, including the 2009 failure in Copenhagen that has shadowed Obama’s climate efforts for the past six years. But they weren’t smooth sailing either.

One U.S. official told POLITICO that even as late as Friday night, the talks were “dicey” — and not just because of the wording error, which a different senior administration official called “understandable in an environment when the French presidency’s staff have been working non-stop through the two weeks.”

Another speed bump was defusing objections from China.

Even though the U.S. had dramatically improved its relationship with China in the last 18 months through a series of one-on-one huddles that produced a joint climate pledge last year by President Barack Obama and Chinese leader Xi Jinping, administration negotiators were haggling with Beijing — and India — into the morning on Saturday, sources familiar with the issue said. The topic was two of the most thorny issues in the negotiations: how to verify that all countries would meet their promises and how to pay for the hundreds of billions of dollars that poorer nations will need to address the threat of climate change.

China is the world’s top producer of carbon pollution and India is No. 3, with the U.S. in the middle, but the two Asian powerhouses are also developing nations that have relied heavily on fossil fuels like coal to try to lift their populations out of poverty.

Todd Stern, Obama’s lead climate negotiator, Obama senior climate adviser Brian Deese and fellow senior White House climate official Paul Bodnar were all spotted on Saturday morning meeting again with Chinese delegates.

China and India frustrated many richer countries when they objected to key provisions in an earlier draft text during closed-door meetings this week. That tense set of meetings set off a new round of diplomacy among the United States, India and China. The final compromise relied in part on assuaging China and India’s worries that they would be held to the same standards as developed countries like the United States.

Several factors helped bring China and India on board with the final deal: frustration over the air pollution in both countries and a sense among senior officials there that they didn’t want to be painted as the villains thwarting a deal aimed at saving the world.

But another factor played perhaps a more decisive short-term effect on the dynamics of the negotiations: the European Union and United States’ strategy of building such a huge coalition of supporters that China, India and its other allies had little choice but to follow suit. The bloc, led by the European Union and the Marshall Islands, wanted a commitment to a stringent temperature goal and strong transparency provisions, among other things.

Obama made an early push to win over island nations — and by extension the other countries that are most vulnerable to the effects of climate change — with a personal meeting with the leaders of five countries, including the Marshall Islands and Saint Lucia. Kerry also had frequent meetings with officials from the island nations, including Tony de Brum, the Marshall Islands’ minister of foreign affairs, and Tuvalu Prime Minister Enele Sopoaga. Kerry and Sopoaga worked together to come up with compromise language on the contentious issue of how to compensate more vulnerable countries for the losses and damage they face from climate change, according to sources.

The United States began talking with an informal coalition of countries fighting for a strong climate deal several months ago, and the discussions progressed during an hours-long dinner in Paris late last week with Stern, EU climate commissioner Miguel Arias Cañete and others. By the end of this week, the coalition’s membership had swelled to well over 100 governments, including the EU, Africa, Caribbean and Pacific island nations, Canada and Brazil, diminishing the collective bargaining power of other negotiating blocs and influential countries like India, China and South Africa. Representatives of those latter countries even griped to reporters that they weren’t formally invited to join the so-called “high ambition coalition.”

And by Saturday, the fierce disagreements that marred behind-the-scenes negotiations had dissipated — at least publicly.

While the French kept their draft deal under lock and key for much of Saturday, the mood in the hallways of the conference center was downright giddy, and the “high ambition coalition” had become the stars of the show.

The United Kingdom’s offices became the makeshift headquarters for the “high ambition” countries, firming up their position before the final gathering of all 176 governments. Stern was met with applause when he entered a meeting there Saturday afternoon.

As the clock nearexxd 11.30 a.m. Paris time, the “high ambition” ministers filed out through the chipboard doors of the office and posed for a group photo. They proceeded to make the slow walk down the winding conference halls, surrounded by a ballooning throng of reporters, negotiators and observers and growing cheers and whistles, and finally filed into a key gathering of negotiators.

“It’s a massive, massive thing. One year of work,” one EU source whispered on the sidelines, punching the air with excitement.

The gentle optimism remained in the hours after Fabius presented his draft text, while negotiators pored over each page to decide whether they would vote it through or not.

India’s environment minister, Prakash Javadekar, strolled by the U.K. office, where a number of coalition members were still meeting, and gave Brazil’s chief negotiator a hug and then shook Stern’s hand. Days of animosity had turned into excitement. The climate agreement was in the bag.

“This is a good agreement,” Javadekar told reporters. Three hours later, the deal was done.

Sara Stefanini contributed to this story.