Two weeks of climate talks organized by the United Nations finished with developing countries demanding more clarity from their richer counterparts on when a promised package of $100 billion in finance will materialize.

Envoys from almost 200 nations are leaving Bonn, Germany, on Thursday without producing a draft negotiating text for ministers to discuss at the end of the year. Instead, they planned another round of negotiations in Bangkok before their annual conference in Poland in December.

The holdup threatens to unravel three years of work to complete the Paris Agreement, a landmark deal reached in 2015 that set out an ambition to limit fossil-fuel pollution in all nations for the first time. Negotiators are working toward writing a rule book that will help bring the pact into force even as U.S. President Donald Trump vowed to withdraw from the Paris framework.

“Sharp political differences remain on a handful of issues, especially on climate finance and the amount of differentiation in the Paris Agreement rules for countries at varying stages of development,” said Alden Meyer, who has been following the talks for more than two decades for the Union of Concerned Scientists. “These issues are above the pay grade of negotiators in Bonn and will require engaging ministers and national leaders.”

Tensions have been building for years on the matter of funding that industrial nations promised developing ones to pay for transforming their economies to run on clean energy — and to cope with the more violent storms and rising sea levels associated with higher global temperatures.

Rich countries led by the U.S. and European Union pledged in 2009 to ramp up climate-related funds to $100 billion a year by 2020. While they have made progress on that commitment, reaching $62 billion in 2014 according to one official study, developing nations want more detail on what money is coming before signing up to the Paris rules.

Developing nations are being asked for more transparency on the emissions they produce — and to open up to some sort of process for verifying that information. Many of them are concerned that will add expensive and cumbersome bureaucracy — or that richer nations will use those tools to limit trade. Richer countries see the rules as essential to making credible the pollution cuts that the Paris deal promises.

“If you don’t have policies that underpin the number that’s been put in Paris, you’ve got nothing to drive progress,” said Elina Bardram, a European Commission official who’s head of the EU delegation at the talks in Bonn.

Developing nations say that a rebound in the cost of carbon emissions in Europe is creating pools of new cash that might come their way. As industrial countries take on tighter emission targets, they may buy traded carbon credits from poorer nations, said Wael Aboulmagd, an Egyptian ambassador who was speaking for the group of developing nations called G77 & China.

“People are anticipating that down the road this is going to be a significant contributor to the balancing of emissions with trade issues and enticement for countries to show more ambition,” Aboulmagd said.

Patricia Espinosa, who leads the UN body organizing the talks, said at a press conference in Bonn that the past two weeks were a “productive session,” although “there continues to be more progress on some issues than others.”

The work of creating a text was supposed to be completed in Bonn and now will shift to another meeting to be convened in Bangkok later this year. The extra time would be used to produce clear options for the end-of-year session in Katowice, Poland, which will be attended by ministers and world leaders.

“We need that Bangkok session, Why? Because no Bangkok session, no deal in Katowice,” said Tosi Mpanu-Mpanu, a representative from the Democratic Republic of Congo. “No deal in Katowice, some guys in the U.S. will be celebrating, saying, we were right to leave this thing.”

Trump has remained mostly silent about the global fight against climate change since June 2017, when he vowed to withdraw from the Paris deal. His predecessor, Barack Obama, strongly supported the talks, with $2.7 billion in climate-related aid in 2014 and a pledge to help capitalize the Green Climate Fund. Trump held up money for the Green Climate Fund, and his officials in Bonn declined to comment to the press.

Richer nations traditionally have used finance for leverage to get concessions they want on transparency from developing nations. Some environmental groups are concerned that strategy threatens to undo the cooperation the UN talks is meant to spur.

“With developed countries refusing to move on finance, lots of pieces are still unfinished,” said Harjeet Singh, who speaks on the issue for ActionAid International, an advocacy group. “This is holding up the whole package. Issues are piling up. It’s a dangerous strategy to leave everything to the last minute.”