By Alister Doyle and Valerie Volcovici

OSLO/WASHINGTON (Reuters) - India will face pressure to speed up its plans for cutting greenhouse gases used in refrigerators, air conditioning and aerosols when governments meet this week to hammer out what would be a third key deal to limit climate change in a month.

About 150 nations meet in Rwanda, from Oct. 10-14 to try to agree a phase down of factory-made hydrofluorocarbon (HFC) gases. U.S. Secretary of State John Kerry will be among those attending.

A quick phase-down of HFCs could be a big contribution to slow climate change, avoiding perhaps 0.5 degree Celsius (0.9 Fahrenheit) of a projected rise in average temperatures by 2100, scientists say.

But India wants a peak in poor nations' rising emissions only in 2031, to give industries time to adapt. More than 100 other nations including the United States, the European Union and African states, favor a peak in 2021.

"It really does matter how early the agreement kicks in," said Jake Schmidt, of the U.S. Natural Resources Defense Council, which reckons India's proposal would add the equivalent of almost a year of global carbon emissions to the atmosphere.

"We must get enough time before the phasing out period starts. We are very clear," Indian Environment Minister Anil Madhav Dave said on Oct. 1, according to the Times of India.

Use of HFCs, which can be 10,000 times more powerful than carbon dioxide as greenhouse gases, is already declining in many rich nations.

An HFC accord would be the third big step this month to curb global warming after the 2015 Paris Agreement for a global shift from fossil fuels gained enough backing to enter into force and governments agreed a deal to limit emissions from aviation.

President Barack Obama, hailing the Paris Agreement at the White House last week, said HFCs and aviation would also help "build a world that is safer and more prosperous and more secure".

The U.S. president has been keen to secure global climate agreements, meant to limit rising sea levels, droughts, floods and heatwaves, as part of his legacy.

Last month, 16 governments including the United States, Japan and Germany and private donors such as Microsoft founder Bill Gates agreed an $80 million fund to help an early phase down of HFCs, hoping to persuade developing nations to sign up.

Many industries are already moving.

"Unlikely as it may seem, a global HFC phase-down is backed both by leading environmental groups and the industry that makes and uses these chemicals," said Frank Maisano, of the U.S. Air-conditioning, Heating and Refrigeration Institute which represents companies such as Carrier Corp or Honeywell.

"We and many others in the industry have started to phase out HFCs. But the process is not completed," said Daniel Frykholm, spokesman for Sweden's Electrolux which wants to halve its greenhouse gas emissions by 2020 from 2005 levels.

The HFC talks are part of the 1987 Montreal Protocol, which succeeded in cutting the use of chlorofluorocarbons (CFCs) to help protect the ozone layer, which shields the planet from ultraviolet rays that can cause skin cancer.

But the HFCs that have often replaced them, while better for the ozone layer, are powerful greenhouse gases.

(Reporting By Alister Doyle; Editing by Raissa Kasolowsky)