Staff at the State-owned Great Southern Hotels are to ballot on industrial action next week over issues arising from the planned sale of the hotels.
About 700 Siptu members are eligible to participate in the ballot, which could give the union a mandate to strike from July 21st.
An intervention by the Labour Court, however, is expected to take place next week.
The eight hotels have been put up for sale as going concerns by their owner, the Dublin Airport Authority (DAA).
Yesterday had been set as the deadline for tenders for any or all of the hotels, but this has been extended to July 28th.
A spokesman for the DAA said the extension was needed because of the volume of tenders received and the level of interest in the sale.
Siptu had asked the company to suspend the sale process until a number of outstanding issues of concern to staff were resolved, but this request was refused by the DAA. The extension may give the parties breathing space to conclude an agreement.
Siptu Killarney branch organiser Donal Tobin said the union had concerns in four key areas, including pensions and the need to protect existing agreements on pay and conditions.
On pensions, for example, Siptu wants a guarantee that staff pension entitlements will be maintained. The DAA says it cannot impose this condition on potential buyers, given that pensions are not covered by transfer of undertakings legislation.
Mr Tobin said any decision on when to implement industrial action, in the event of members voting in favour of that option, would be a matter for the negotiating committee involved, in consultation with Siptu's national executive.
However, the union would have the right to serve a week's notice next Friday, when the ballot concludes, of action to begin on July 21st.
Talks at the Labour Relations Commission broke down late last month. Mr Tobin said an invitation to attend the Labour Court was expected.
The DAA spokesman said it had been the company's position from the outset that the parties should attend the Labour Court without preconditions. He claimed that Siptu had been unwilling to do so unless the sale process was suspended.
Workers employed by the hotel group have been offered the option of a severance package or retention of their jobs after a sale of the hotels. Those leaving would receive eight weeks' pay per year of service, while those who chose to stay would receive a "loyalty payment" of six weeks' pay for every year worked. The "loyalty payments" would be taxed less favourably than redundancy pay.
The Great Southern group has hotels at Dublin, Cork and Shannon airports, as well as two each in Kerry and Galway and one in Rosslare, Co Wexford.