Spanish Prime Minister Pedro Sanchez on Thursday offered Madrid as a replacement venue for the United Nation's COP25 conference to tackle unresolved issues on how to globally slash climate-disrupting carbon emissions.

Last year's UN climate conference drew 20,000 experts to Katowice, Poland.

Patricia Espinosa, Executive Secretary of the UN Climate Change secretariat (UNFCCC) based in Bonn, said Spain's offer was an"encouraging" sign of multilateralism and would allow organizers to stick to the summit's original timetable.

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It was not immediately clear on what scale a Madrid event from December 2 to 13 could take place, given the logistical challenges.

A UNFCCC spokesman an official letter from Spain was still awaited. A meeting between Spanish and UN officials would be held in Bonn, possibly on Friday.

'Common sense,' says Pinera

On Wednesday, Chile's right-wing billionaire president Sebastian Pinera cancelled his county's plans to host both the UN climate summit as well as an Asia-Pacific APEC economic summit in November.

Pinera, facing deadly unrest involving protesters angry about the gap between rich and poor, deficient healthcare, and education, said the conference cancellations were "painful" but driven by "common sense."

Announcing Spain's offer on Thursday in Santiago de Chile, Pinera described Sanchez's offer as "generous" and said it would still enable climate experts to meet and focus on "all the progress that had been achieved."

Sanchez is currently Spain's interim leader, pending a general election on November 10.

COP25 would be the latest in a string of technocratic meetings known in UN terminology as the Conference of the Parties to the United Nations Framework Convention on Climate Change (UNFCCC).

ipj/aw (Reuter, AP, AFP, dpa)