CFMEU northern mining president Peter Jordan said the wage increase on offer was $45,000 less a year than what Idemitsu paid to employees at their open cut mine in Muswellbrook.

Mr Jordan said the union wants the same pay packet, bonus structure, access to independent arbitration and sick day arrangements the company has with its Muswellbrook and Ensham workers.

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"We would have thought based on those conditions being agreed upon at the other two operations, those matters would be resolved straight away," Mr Jordan said.

"Idemitsu's workers are already afforded the same conditions at its other mines, so what we're proposing are not unreasonable expectations.

"It is frustrating. At the end of the day, we would like to have all the issues resolved as soon as possible. That's what the union wants and that's what our members want."

Only one of the sticking points - a change in rosters that would encourage fly-in/fly-out workers - has been resolved.

"The company has now agreed to include words to the effect that any new roster must be agreed upon by the majority of the workforce," Mr Jordan said.

"We're yet to see those words included in the agreement, but we hope to see them in the next meeting."

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Union officials will meet with Idemitsu later this week and if there's no progress, workers will step up their strike action.

"We engaged in eight- and 10-hour stoppages last week, and currently we're engaging in regular two-hour stoppages this week," Mr Jordan said.

"If nothing has been resolved after this meeting, we're proposing to have a 48-hour stop work meeting and bring all the members together for a mass meeting in Gunnedah."

Mr Jordan said the conditions being fought for had already been in place under the previous mine operator, Downer Group.

"So not only are we trying to get back what they already had, to make it worse, Idemitsu has already agreed to these conditions at its other two mines," he said.

A spokesperson for Idemitsu said the company was "negotiating in good faith" and "proposing a number of improved employee benefits".

"Our understanding is this has not been communicated by the CFMEU to all of its members," the spokesperson said.

"On that basis we are surprised the CFMEU have taken further industrial action.

"The CFMEU should be focused on genuinely negotiating with us to come to an agreement for the benefit of all Boggabri Coal employees.

"We will continue to communicate directly with our workforce and their representatives in an effort to reach an agreement that is mutually beneficial to all parties."

This week marks a month of periodic industrial action by the mine's workers.