Public service association (PSA) regional organiser Stephen Mears conceded that their first 24-hour strike in a decade would be disruptive, but said the public understands the need for the action.

"It's short-term pain for long-term gain, and it's not just about salaries. Part of that is the industrial relations system has been hog-tied by the current government," he said.

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"We could run a wages case and maybe get an agreement of the 5.2 per cent or more, but the commission has been hamstrung as the independent umpire because they can only pass on the government's policy of wage increases."

The public sector union has followed the unions representing teachers, health workers, paramedics and more in taking industrial action to press for better pay rises.

On Monday the government announced it would offer a 3 per cent pay rise this year, but that would still significantly slash wages in a range of public sector workplaces, in real terms.

Mr Mears said the strike could disrupt both the courts and jails.

"[With] prison officers, generally what they do is a lockdown and a skeleton staff can run the jail. They're very industrially-orientated. I think our density in the correctional facilities is about 98 per cent," he said.

A spokesperson for the Department of Communities and Justice said that some court sittings will be affected due to industrial action on Wednesday, without going into specifics.

"The local and children's court are proceeding where possible," they said.

"All district court matters listed on 8 June will be adjourned to 9 June."

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The union expects between 70 and 100 staff to walk off the job on Wednesday, including employees at legal aid, community services, juvenile justice, court sheriffs and other staff, school administrative staff, and police administration staff. Police radio staff are covered by the PSA, but won't strike for safety reasons.

Thousands are expected to strike statewide, in the 24 hour industrial action.

The unionists will rally near the electorate office of Tamworth MP Kevin Anderson, who will be at parliament in Sydney on Wednesday, and then march through the streets of Tamworth, before holding a stop work meeting.

Mr Mears said cutting the wages of public servants would disproportionately affect rural communities - and many workplaces are significantly understaffed as a result of uncompetitive pay.

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Out of 48 unsworn positions at Tamworth's police radio service, the service is 12 staff short, he said.

Without a resolution, he predicted further industrial action, which might mean further days of strikes.

"We're trying to do the least effect on the public as possible, but also trying to get our point across that the increases over the last several years have been extremely poor, notwithstanding the current one as well," he said.

"This 3 per cent also includes the employer contribution to superannuation of 0.5 per cent. That will come out our members' pay rise."

Health staff will receive a one-off $3000 bonus from the state in this month's budget - which Mr Mears dismissed as a "Christmas present" - but other public servants won't even get that.

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On Monday, Treasurer Matt Kean said the increase in wages was fair and sustainable in the current economic climate.

"NSW is currently enjoying the lowest unemployment on record and it is important to maintain competitive wages to attract and retain the best talent. In the context of a strong and growing economy this two-year increase to wages is an affordable and sensible policy," he said, on Monday.

Skeleton crews will be left on staff at all essential services.

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