Rich nations are dismaying developing countries with pledges merely to continue aid to help them combat climate change in 2013 despite past promises of a tenfold surge to $100 billion a year by 2020.
"There should be a transparent process to scale up finance" towards 2020, said Seyni Nafo of Mali, spokesman for the 54-nation African group at UN negotiations. The poor needed more than "an indication that funding will not fall off a cliff".
A looming gap in aid pledges after a 2010-12 "fast start" programme of $10 billion a year is a big source of tension before UN talks in Qatar from November 26-December 7 meant to review progress towards a deal to fight global warming, due by 2015.
The problem dates back to a UN summit in Copenhagen in 2009, when leaders including President Barack Obama agreed the fast start programme and set a separate goal of $100 billion in annual aid by 2020 to help the poor to slow global warming.
But no one spelled out what would happen from 2013-19.
Now, with many donors struggling with economic crises, there is little spare cash for climate aid, funds meant to help poor nations to curb rising greenhouse gas emissions and adapt to droughts, floods, heatwaves or rising sea levels.
Major donors - the European Union, the United States and Japan - are only giving reassurances about continued aid for 2013, without firm numbers. And they are putting off any surge.
"Finance is key to agreeing on a package at Doha," said Pa Ousman Jarju of Gambia, chair of the 48-nation group of least developed countries. He expressed hopes for "renewed US action on climate change" after Obama's re-election.
Small island states want "scaled-up, new and additional, predictable and adequate climate finance" from 2013, said Samoa's ambassador to the UN, Aliioaiga Feturi Elisaia.