By Alister Doyle, Environment Correspondent
OSLO, Sept 18 (Reuters) - A U.N. summit on climate change next week will test rich nations' willingness to fill a near-empty fund to help the poor, but pledges are likely to be far short of developing nations' hopes for $15 billion in 2014.
Emerging nations say that cash for the Green Climate Fund (GCF), meant to help the poor with projects to curb rising greenhouse gas emissions and adapt to heatwaves, floods and rising seas, is vital to combat global warming.
U.N. Secretary-General Ban Ki-moon wants more than 120 world leaders to make "bold pledges" about climate change at the Sept. 23 summit in New York.
Many rich countries have indicated willingness to fund the GCF but German Chancellor Angela Merkel is the only leader so far to make a large contribution, pledging $1 billion over four years in July.
"A number of countries are working very hard to try to ... make the announcements in New York," said Hela Cheikhrouhou, head of the GCF which opened headquarters in South Korea in 2013.
"We think some of them will do so, and several more are likely to more broadly state their support," she said. A separate GCF donors' conference will be held in November.
Many rich nations are struggling to maintain aid budgets as they focus on spurring growth and jobs at home.
Before Germany's announcement, pledges to the GCF totaled just $55 million from 12 nations, according to the World Bank. And no other rich nations are signaling vast new outlays.
Norway's Prime Minister Erna Solberg told Reuters that she would pledge 200 million crowns ($31 million) at Ban's summit, for 2015 alone. That is less than many environmental groups have been hoping since Oslo is often among the most generous donors.
GCF funding is part of an increasing squeeze for developed nations, which set a goal in 2009 of channelling an annual $100 billion from 2020 to help the poor cope with climate change, made up of funds from both private and public sources.
They agreed a "significant" share will go via the GCF.
Meena Rahman, of the Third World Network development group, said countries including the United States, France, Britain, Italy, Sweden, Switzerland, Finland, the Netherlands and Denmark indicated at a GCF meeting last week that they will make pledges this year, but not necessarily at Ban's summit.
Developing nations want promises of $15 billion for the GCF in 2014. Peru, due to host a U.N. climate conference in December, has set a less ambitious target of $10 billion.
Aid charity Oxfam said that indicative shares, if developed nations were to give $15 billion, include $4.8 billion for the United States, $6 billion for the European Union, $2.3 billion for Japan and $600 million for Canada.
Developing nations want clear signs of increasing funds towards 2020 to encourage them to join a U.N deal, due in late 2015 at a summit in Paris, to slow global warming.
"Climate finance is not only crucial for unlocking a deal, it is an indispensable part of bringing emissions down and helping vulnerable communities adapt," said Marlene Moses, of Nauru, chair of the Alliance of Small Island States.
Moses said the poor wanted clear signs of funds in New York.
The U.N. panel of climate experts says it is at least 95 percent probable that mankind is the dominant cause of global warming since 1950. Many voters are doubtful, reckoning natural variations are to blame and complicating efforts to crack down.
(Additional reporting by Ben Garside in London; editing by Ralph Boulton)