Five hundred job losses over the next three years at Carmarthenshire council are a "worst case scenario", the authority says.
A letter has gone to all staff asking them for different ways of working as it looks to make savings of £28m.
Local politicians warned that the job losses would be a "hammer blow".
But executive board member Councillor Philip Hughes said none were planned this year.
Mr Hughes, executive board member for people management and performance, said: "Losses of 500 jobs are our worst-case scenario, as are large-scale compulsory rendundancies.
He added at most 160 jobs a year would be lost over three years.
He said they believed those cutbacks could be achieved through natural wastage and voluntary cutback of hours or early retirement.
"Our aim is to work with staff to first of all establish whether there is any interest in a change of their working patterns which could generate savings," he said.
Carmarthenshire, like all other public sector organisations, was facing budget difficulties, Mr Hughes said.
"But we are a forward-looking council, and we have two options - either to plan ahead and work with our staff and unions or wait until we are forced to make changes," he added.
Earlier Paul Thomas, Carmarthenshire assistant chief executive, said that while no compulsory redundancies were planned for the year ahead, there would be reductions in some services when staff leave or retire.
"Unless we are able to find different ways of providing services at less cost, or are able to reduce the cost of services in general, it is inevitable that further job losses will be needed," he said.
Mr Thomas said the council had written to its staff asking if they would be interested in flexible working options such as reducing their hours, career breaks and voluntary early retirements for those aged over 55 by March 2011.
"All departments have been working towards identifying potential savings of 12.5% over the next three years, and this work is ongoing."
Local AM and MP Rhodri Glyn Thomas and Jonathan Edwards have both expressed their concern .
Mr Thomas, Plaid Cymru AM for Carmarthen East and Dinefwr, urged the council to explore all other possible avenues for making savings before resorting to job cuts.
"I will be taking this matter up with the Welsh Assembly Government in order to ensure that everything is done from that end in terms of seeking to increase job opportunities and training in the county," he said.
Jonathan Edwards, Plaid's MP for the same area, said: "There is already a high level of unemployment in the county and so clearly talk of slashing anything up to 500 jobs will be a hammer blow.
"What is certain is that these job cuts should not be a bulk cull of the lowest-paid employees. The council will need to look at its approach holistically with cut backs being targeted also at remuneration packages of senior officers."