A controversial mine extension sought by two coal giants in NSW's Hunter Valley still stands despite paperwork being abruptly withdrawn.
Hunter Valley Operations (HVO) was seeking approval to extend the life of its two adjacent mines near Singleton before a legal challenge by local environmentalists.
Jointly owned by Yancoal and Glencore and supplying global and domestic markets, the mines produce thermal coal to be burned in power stations to generate electricity and metallurgical coal for making steel.
Under the initial proposal, HVO North - slated to close in 2025 - would be mined until 2050 and HVO South would get a 15-year extension to 2045.
A company spokesman said the NSW government had asked for more information, which would require detailed modelling, so it made sense to withdraw from a federal process.
To give certainty to hundreds of workers, an initial one-year delay to June 2026 on any decision would be sought, he told AAP on Friday.
In June, the Hunter Environment Lobby took legal action to overturn a federal decision that allowed the project to move to the next stage in federal environmental approvals.
Critics said it would be permitted to extract an additional 400 million tonnes of coal that when burned would have added 1.16 billion tonnes of greenhouse gas emissions to the atmosphere.
Lawyers for the lobby group said legal action was being discontinued before the case could be heard by the Federal Court, as HVO was withdrawing the application and submitting an amended plan.
Yancoal's Ashton Ravensworth coal mine extension was approved in September by Environment Minister Tanya Plibersek, along with two others in the Hunter Valley.
Environmental campaigner Jan Davis said it was not clear what changes HVO planned to make to its development application.
"There is nothing they can do that change the basic fact that coal mining is pumping billions of tonnes of carbon pollution into the atmosphere, which is driving catastrophic changes to our climate and more extreme weather," she said.
"We will watch very closely to see what moves the company makes next."
Lock the Gate Alliance spokeswoman Carmel Flint said on Friday global mining giants should not be able to recklessly endanger the climate.
She said the "monster" project would have shifted the responsibility for action on climate onto other sectors of the economy, including agriculture and manufacturing, and made insurance premiums even more expensive.
"The withdrawal of the federal referral underscores that this was an ill-conceived project from the outset," she said.
