Emergency plans are in place to ensure the postal service continues to deliver with strike notice due to expire today.
The postal company said the Communications Workers Union (CWU) had refused to give any details of the type, location or duration of the industrial action being planned for the coming days.
“The CWU refusal to provide any information on the nature and timing of the action makes it extremely difficult for An Post to advise customers or to put in place arrangements to minimise the impact of that action,” the company said.
The company said the trade union had refused all demands for casual staff to be hired in Dublin.
With the strike notice ue to expire today, concern has been deepening over the effect of a postal strike on businesses and the public in the run-up to Christmas.
The CWU has accused An Post of failing to pay cost-of-living increases to workers and pensioners under the Sustaining Progress national agreement.
The Labour Court has already recommended that three other unions at An Post who represent managers should get backdated pay increases due under Sustaining Progress for agreeing to work changes.
The company said it was putting in place all possible contingencies available to the company to minimise the level of disruption to customers, to ensure, where possible the payment of pensions and other social welfare benefits.