The Construction, Forestry, Mining and Energy Union is still considering industrial action at Illawarra BHP Billiton mine sites as employees face worsening job security.
A union spokesman confirmed the move despite reports the union had "shelved" an industrial campaign in the weeks before Illawarra Coal, a subsidiary of BHP, sacked 85 workers on July 4.
Claims the industrial action had been shelved were reported on Monday in industry publication International Coal News.
It said the action was to have included measures such as taking an unlimited number of 24-hour work stoppages, banning the use of diesel vehicles underground and limiting longwall production to one shear per shift.
CFMEU south-western district vice-president Bob Timbs rejected the report, and said industrial action was still on the cards.
"We're continuing to negotiate with the company in the hope of delivering a positive outcome," he said.
"The report that industrial action has been cancelled is incorrect - at some stage we may use industrial action, but at this stage we will continue to negotiate with the company."
Mr Timbs said workers were concerned for their future following the recent round of job cuts.
"Our core issue is security of employment," he said.
"It's across the board - everyone has fears for security of employment."
BHP owns three mines in the Illawarra - Appin, West Cliff and Dendrobium.
At the time of the cuts, Illawarra Coal president Troy McDonald blamed the decision on "difficult market conditions, including continuing low coal prices and oversupply".
"The industry is also undergoing a difficult transition, and to be globally competitive the cost base of our operations must be reset," he said.