The NSW government recently signalled the Vickery project, located between Gunnedah and Boggabri, was near the end of its assessment process and will soon be handed over to an independent body that will make the final call.

Whitehaven has also deferred decisions about expanding its existing underground mine near Narrabri and developing its proposed Winchester South mine in Queensland.

"While coal markets in the March quarter have demonstrated their resilience, volatile financial market conditions caused Whitehaven to continue to be cautious in allocating capital to expansion," the company said.

"Whitehaven does not expect to consider making a final investment decision in relation to these projects in 2020."

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During the March quarter, Whitehaven spend $6.9m on studies and designs for its expansion projects.

Lock the Gate Alliance spokesperson Georgina Woods called on the company to formally scrap the proposal.

"Whitehaven sounds very uncertain about whether it will proceed with this mining project, and we heartily and sincerely hope they do not," she said.

"The company should do the honourable thing and withdraw the project, rather than leaving it to linger over the lives of locals in the Boggabri district.

"The Vickery coal mine will damage local groundwater, put an iconic heritage property at risk, and worsen the social damage large-scale mining has already inflicted on the local community."

Several of the company's mines saw a drop in production during March due to heavy rains, while there was a 20-day outage at Narrabri due to issues with the mine's longwall.

Whitehaven also introduced a fleet of six autonomous haulage trucks and excavators at Maules Creek mine, which are expected operate seven days a week by the end of the financial year.