Ms Ley has delayed her decision on the controversial project until October 30. She was initially was set to hand down her verdict on September 8, but pushed that deadline back until October 13 before the most recent extension.

A spokesperson for the Department of Agriculture Water and the Environment said the time frame will allow for the completion and consideration of additional site survey work.

The state government approved the quarry expansion in July but federal environment minister Susan Ley will have the final say on whether it can go ahead.

Wildlife researchers and the Brandy Hill and Seaham Action Group have argued the area of the proposed extension is an important koala habitat.

Save Port Stephens Koalas campaign manager Victoria Jack said while campaigners were exhausted from their fight to stop the extension, they would keep the pressure on the government to reject the decision.

"We don't intend to stop," Dr Jack said. "We have to keep this on the agenda and keep raising awareness."

Meanwhile, Canadian singer K.D. Lang has weighed in on the saga, tweeting her support for the Save Port Stephens Koalas movement.

"Due to the bush fires, koalas are on a steep decline and are facing extinction in New South Wales, due to habitat loss & fragmentation," she tweeted.

"To save koalas Australian gov must act now to prevent their homes from being bulldozed. #saveportstephenskoalas #stopbrandyhill @sussanley"