Australia is increasingly out of step with the other nations attending the G20 summit in Brisbane as yet another major economy takes concrete steps to addressing climate change.
Japan has announced plans to give up to $1.5 billion to the UN-backed Green Climate Fund (GCF) to help developing countries fight global warming, a report said Friday.
Prime Minister Shinzo Abe is expected to announce the pledge at the G20 meeting, undermining Prime Minister Tony Abbott's decision to keep climate change off the G20 agenda, Kyodo News agency reported, citing sources close to the matter.
The cash will come on top of a reported $2.5 billion that Washington is stumping up for the GCF, a mechanism designed as a way for wealthy countries to help poorer ones to become greener and to bolster their defences against the effects of climate change.
France and Germany have also pledged to contribute $1 billion each to the UN's new climate framework.
Christiana Figueres, the head of the UN Framework Convention on Climate Change (UNFCCC), has called for an initial capitalisation of $10 billion by the end of the year.
Mr Abbott says despite the climate focus by other nations the G20 will continue to focus on economic issues and not climate change.
The G20 summit is the third event in an intensive week for international meetings, and comes after US President Barack Obama and China's President Xi Jinping agreed a deal that would see both countries - major polluters - curb their emissions.
The US says it will cut emissions by 26 to 28 per cent by 2025, while China has set a goal for its emissions to peak in 2030.
Australia is aiming for a more modest five per cent cut by 2020.
Mr Abbott says the G20 is the world's premier economic conference and he expects the focus will be on economic reform and economic growth.