BONN, Germany — The lack of green is fouling up efforts to hit ambitious targets to reduce pollution — green, as in money.

The traditional fight between rich and poor countries over the best approach to climate change has hit a fresh diplomatic impasse. As the clock ticks down to a key international summit in December, the key sticking points are who's (more) responsible for advancing the fight against climate change and, crucially, who picks up the tab.

International negotiations in Bonn this week were meant to pave the ground for a deal on how to implement the Paris accords at the global climate summit in Katowice, Poland. They wrapped up Thursday without much progress.

The December summit has been hailed the most important since nearly 200 governments agreed the landmark climate accord in Paris in 2015. And it is there in Poland that governments are supposed to sign off on rules setting out how countries monitor and report their emissions cuts and increase their climate efforts over time.

“What else? Money talks,” said Amjad Abdulla, a delegate from the Maldives and chief climate negotiator for the Alliance of Small Island States. He added that promised emissions cuts on the table now fall far short of meeting the Paris deal's temperature goals of keeping global warming to well below 2 degrees, and as low as 1.5 degrees.

“Bold commitments to the Green Climate Fund would be a massive trust-builder for developing countries” — Tracy Carty, Oxfam International

"If you look at the [climate commitments] from the global south, it’s mostly conditional on the provision of finance," Abdulla said. "We will do what we can, but there are limitations. That’s the message we want to convey."

Developing countries want greater clarity, or predictability, on the financial flows they can expect from rich countries in the future.

The developed countries and the EU want the rules to establish a common system that allows countries to compare and verify emission cuts and other climate efforts.

Patricia Espinosa, the U.N.'s climate chief, told reporters on Thursday that both finance and agreement on robust rules are needed. "Finance is no doubt an important issue," she said. "At the same time, finance, by itself, will not be the solution."

She said she has repeatedly raised the "need to make sure there is clarity about ... the commitments that have been made already [by developed countries]."

One long-standing issue, causing frustration among developing countries, is for rich nations to meet a pledge to provide climate finance worth $100 billion annually by 2020.

“We need a package on finance issues to provide clarity on how developed countries will meet [that goal]," Alden Meyer of the Union of Concerned Scientists said. “There’s tremendous gridlock on … how and when developed countries will provide more upfront clarity on their financial support for developing country action.”

Vulnerable countries want the developed world to ensure it will increase its efforts to cut greenhouse gases and provide cash to those in danger from future impacts such as sea-level rise. The announcement of President Donald Trump to withdraw the U.S. from the Paris climate agreement has undermined confidence that industrialized countries mean business.

Delegates late Wednesday agreed to schedule an additional negotiation session in Bangkok in September, to achieve further progress on working out the technical details of the agreement.

Threats to make agreement on robust rules in Katowice contingent on more money flows haven't gone down that well with European negotiators.

"It felt like nothing was getting done," said one observer close to the Bonn talks. "It felt like slow death over the last week.”

Long way to Katowice

The EU knows that money will help unlock the stalemate and absent U.S. financial and diplomatic support, there's a lot of pressure on the bloc to deliver. The European Commission is already looking for ways to sweeten the pot for developing countries, with the head of its climate department last month calling on EU ministers to consider replenishing climate funds.

But threats to make agreement on robust rules in Katowice contingent on more money flows haven't gone down that well with European negotiators.

The EU says that a common set of rules will glue the Paris deal together and reassure governments, including vulnerable and developing countries, that efforts are happening around the world. The system would give enough flexibility to differentiate between varying capabilities of countries, according to negotiators.

"We need language that allows us to say one ton of CO2 emitted in China is the same as in Brazil, as in the EU," said Elina Bardram, the head of the EU negotiating team in Bonn. Decades of economic growth no longer justify traditional divides between global south and north. "Bifurcation is not something the EU can accept. It's not the 1990s. We've moved on from that."

“In our view, it’s not going to be possible to put off these discussions to 2019 and expect to get the robust package on other fronts we need to get out of Katowice” — Alden Meyer, Union of Concerned Scientists

Not all developing countries agree, including emerging powers such as China that are wary of formal international pressure on their economies. They prefer to keep a system that differentiates responsibilities more clearly between developed and developing countries. Rifts on that question reopened at the climate talks in Bonn last year in a break with the effort in Paris to paper over the issue by allowing countries to come up with their own climate commitments.

The EU is pushing back but getting ready to go some way toward meeting developing countries' financial demands. Raffaele Mauro Petriccione, who heads the Commission’s climate action department, in April already warned that making a deal in Katowice dependent on money — "a blunt approach" — will not be acceptable. "But the EU needs to be ready to consider what margins do we have on this issue of finance,” he said.

Observers at the talks here said that financial gestures are a must if developed countries want their deal. "In our view, it’s not going to be possible to put off these discussions to 2019 and expect to get the robust package on other fronts we need to get out of Katowice," Meyer, from the Union of Concerned Scientists, said.

One gesture that could go a long way to build confidence, observers said, is to replenish the Green Climate Fund, set up to support developing countries in their climate efforts. "Bold commitments to the Green Climate Fund would be a massive trust-builder for developing countries," said Tracy Carty of Oxfam International.

But that decision can only be taken by ministers.

"Ministers have to intervene and provide assurance that they will be able to provide the money, and that cannot be resolved at technical level," said Mohamed Adow of Christian Aid.