Talks are moving forward but the parties are yet to reach a resolution.

"We've been meeting deep into the evening and in the early hours of this morning," Mr Park told media on Tuesday.

"This is a challenging process, we know that we are working through multiple layers within a complex award."

As a result of progress being made, an arbitration session with the Industrial Relations Commission scheduled for Tuesday afternoon was held over, a Health Services Union spokesperson said.

Premier Chris Minns also stepped up to the negotiating table overnight, meeting with HSU NSW Secretary, Gerard Hayes.

Mr Hayes said in the union's view the dispute needed to be resolved by the first half of this week.

"We're getting closer to midnight every day," he said.

"The industrial commission's best efforts will go some way, but it will not resolve the issue that we have."

Mr Hayes urged the government to come back to the table on Wednesday morning with all the relevant decision makers and remain there until a deal is done.

"I think this needs to be sorted out by the leadership of the government and the leadership of the union with their respective representatives," he said.

The HSU is seeking a 20 per cent pay rise for paramedics to put them in line with their interstate counterparts.

Mr Park said he was dealing with an already strained health budget and previously offered the union a 19 per cent pay increase which it turned down.

But Mr Hayes said the negotiations were a "once-in-a-lifetime recognition of professional abilities, professional qualifications and professional scope of practice".

"They're not ambulance drivers, their whole quantum has changed. That's why we're dealing with this as a one-off," he said. 

"This won't be coming back over and over again."

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