Port Kembla Coal Terminal workers will remain on the picket line after deciding to strike until Monday.
And the coal terminal has not ruled out further lockouts of its employees.
Combined with an earlier week-long strike it means the workers have not set foot inside the coal terminal since January 19.
That's a total of 30 days without a pay cheque.
Bob Timbs, CFMMEU's district vice president, said the decision to strike for four days was made on Wednesday night.
"We're just resolved to the fact that we’re going to have to finish this, that we need to maintain our current job security clause," Mr Timbs said.
"If it takes further industrial action then unfortunately we’re going to have to do it, but we're prepared to stick it out for the long haul."
Mr Timbs said the strike was prompted by the coal terminal management refusing an conciliation offer from the Fair Work Commission (FWC).
At the heart of long-running dispute is a clause in the enterprise agreement that stops PKCT from retrenching workers and replacing them with contract labour.
The CFMMEU claim PKCT want to remove that clause so they can replace the workers, while the company denies that is the intention.
Mr Timbs has said contract labour was being used inside the terminal while workers were on the picket line, but he still felt a strike would have an impact on the company.
"It will have some effect," he said.
"They’re obviously not maintaining it properly, when they're doing our jobs they’re not doing their own."
A coal terminal spokeswoman said it had advised the CFMMEU it was open to further conciliation in the FWC, but only before Deputy President Booth.
"Friday’s offer for conciliation was before another Commissioner of the FWC who has not been involved in earlier conciliation," the spokeswoman said.
The spokeswoman said the possibility of further lockouts could not be ruled out.
"PKCT is hopeful that employees return to the workplace and we are able to reach agreement with them, which is in the best interest of themselves and their families," she said.
"However, PKCT has contractual obligations in relation to safe and timely ship loading.
"The union’s continued refusal to rule out ongoing action and its rejection of a moratorium to progress negotiations may mean that PKCT will be required to lock out employees to meet its contractual obligations."