Up to 1,000 staff at Newry, Mourne and Down District Council (NMDDC) will strike on Thursday after talks "collapsed" over pay equality, unions have said.
In a joint statement on Wednesday, the four unions representing workers said the industrial dispute was "avoidable".
They said action could be averted if council management addressed concerns.
The strike action is expected for all services other than facilitating funerals and weddings.
The council said it was is disappointed the unions were continuing with plans for strike action but respected their right to do so.
"Newry, Mourne and Down District Council remains fully committed to resolving this dispute, to ensuring fair pay, transparency and equality for all its employees and to delivering value for money for all rate payers in the council area, especially at a time when many are experiencing significant financial hardship," a spokesperson said.
"The council will continue to engage in dialogue with the trade unions to find a workable solution as quickly as possible."
The unions said progress had been made, but a long-running dispute over pay remained unresolved.
Unions Unite, GMB, Nipsa and Siptu said senior management had delayed dealing with the wages of lower-paid workers since the merger of the two former councils, while benefiting from their own being raised.
The statement said staff were "just asking for some recognition of our members' contribution since the establishment of the new council".
Workers are expected to join socially-distanced picket lines at Monaghan Row Council Offices and Greenbank Council Depot in Newry, and Downshire Civic Centre and Strangford Road Depot in Downpatrick from 06:00 GMT Thursday.
NMDDC is one of Northern Ireland's largest council areas with about 180,000 residents.
It includes Newry, Downpatrick, Crossmaglen, Newcastle, Warrenpoint, Saintfield and Ballynahinch.
Jobs saved through redeployment
Separately, Antrim and Newtownabbey Council has said it is "confident" it can avoid the need for compulsory redundancies in its ongoing effort to cut costs.
Back in July, the council announced it would begin to cut 68 full-time jobs, explaining it needed to reduce its expenditure because of the "economic crisis" caused by the Covid-19 pandemic.
But on Wednesday, the council said it had "identified a number of suitable vacancies and redeployment opportunities" for staff affected by the proposed redundancies.
"The significant trade union contribution throughout this entire process has been recognised and appreciated by the council during these unprecedented and challenging times," the council added.