Miners from Helensburgh's Metropolitan Colliery will continue to strike over the weekend after they walked off the job for 48 hours on Wednesday.
CFMEU south-western district vice-president Bob Timbs said about 200 workers at the Peabody Energy mine were expected to end their strike late last evening.
However, they would take further industrial action over the weekend.
The initial stoppage followed three days of bans and limitations by workers after ongoing negotiations over the workers' enterprise agreement came to a halt.
With discussions still unresolved, workers were planning more lawful industrial action from tonight, Mr Timbs said.
He also said some miners had been working during the past few days to ensure the stability of the longwall.
"[On Thursday and Friday] we went in with a skeleton crew and operated the longwall to ensure it was in a geologically sound condition," he said.
A Peabody Energy statement sent to the Mercury yesterday said the company was "disappointed the workforce has decided to take industrial action at this time".
"Peabody Energy Australia has been working with the bargaining representatives at the Metropolitan mine in an attempt to negotiate a new enterprise agreement which reflects current market conditions, lifts productivity, reduces costs, enhances safety and provides greater job security for Metropolitan mine employees," the statement said.
"We remain committed to continuing discussions with the bargaining representatives and workforce."