Marathon U.N. climate talks ended Sunday with a slim compromise that sparked widespread disappointment, after major polluters resisted calls for ramping up efforts to keep global warming at bay and negotiators postponed debate about rules for international carbon markets for another year.

Organizers kept delegates from almost 200 nations in Madrid far beyond Friday's scheduled close of the two-week talks. In the end, negotiators endorsed a general call for greater efforts to tackle climate change and several measures to help poor countries respond and adapt to its impacts.

U.N. Secretary-General António Guterres said he was "disappointed" by the meeting's outcome.

"The international community lost an important opportunity to show increased ambition on mitigation, adaptation and finance to tackle the climate crisis," he said. "We must not give up and I will not give up."

The final declaration cited an "urgent need" to cut planet-heating greenhouse gases in line with the goals of the landmark 2015 Paris climate change accord. But it fell far short of explicitly demanding that countries submit bolder emissions proposals next year, which developing countries and environmentalists had demanded.

Climate Change Minister James Shaw told Mike Yardley developing countries don't feel like the world's lived up to the agreement.

"Most of the developing world signed up to pretty stringent carbon reduction on the basis that they were going to the support to transition, and they don't feel like that's been forthcoming."

He says the consensus was more countries need to take more action.

"They are saying let's crank up for next year. We're just going to have to take a look at New Zealand and see what that would mean for us."

Some observers welcomed the failure of a deal on carbon markets, though, and the European Union and developing countries had said beforehand that no deal was better than a bad one.

"Thankfully, the weak rules on a market-based mechanism, promoted by Brazil and Australia, that would have undermined efforts to reduce emissions, have been shelved," said Mohamed Adow, director of Nairobi-based campaign group Power Shift Africa.

Helen Mountford, from the environmental think-tank World Resources Institute, said that "given the high risks of loopholes discussed in Madrid, it was better to delay than accept rules that would have compromised the integrity of the Paris Agreement."

The talks in Spain took place against a backdrop of growing worldwide concern about climate change. The past year saw large protests in hundreds of cities around the globe and climate activists staged several rallies inside and outside the conference venue to express their frustration at the slow pace of the talks.

Under the Paris accord, countries are supposed to regularly review their national emissions reduction targets and increase them if necessary. Last week, the European Union agreed a goal of becoming carbon neutral by mid-century, but the move did little to sway discussions in Madrid about setting more ambitious targets in the medium term, an issue that will be on the agenda again in Glasgow.

The United States will be excluded from much of those talks after President Donald Trump announced the country's withdrawal from the Paris accord, a process than comes into force Nov. 4, 2020.

Scientists said the longer countries wait to cut emissions, the harder it will be to meet the Paris temperature target.