The proposed Carmichael mine in central Queensland would become the country's largest mine, and is supported by both the Queensland and Australian governments.
But there is opposition from indigenous and environmental groups, who say it would have devastating environmental consequences, including for the fragile Great Barrier Reef.
The co-ordinator of the Pacific Islands Climate Action Network, Krishneil Narayan, said his organisation was joining the opposition because it would affect the Pacific, too.
"It's very relevant because of the impact that it has on climate change. If the coal mine opens it would release a lot more carbon dioxide from the coal that is being burnt."
"It's relevant for the Pacific because we are here trying to limit the impacts of climate change," he said.
"Pacific governments have been calling for an end to fossil fuel extraction," Krishneil Narayan said.