Planned strike action at An Post is to be postponed for a week after a deal was agreed at talks between the two sides tonight.
The National Implementation Body (NIB), which chaired the discussions, said it needed to get an independent assessment of the costs of work practice changes involved in the dispute.
In a statement, it said that it had recommended that tomorrow's industrial action by 8,500 postal workers - which involved a nationwide ban on overtime working and all-out strike action at the GPO in Dublin - should be deferred until the costing is completed in a week's time.
The Communications Workers Union said it would refer the deal to its 12-member national executive tomorrow morning.
"We'd expect the executive will accept that and that will allow the industrial action to be postponed by default," said national officer Sean McDonagh.
However, the industrial action will begin at midnight and continue until the executive makes its decision tomorrow morning.
The CWU has accused An Post of failing to pay cost of living increases to workers and pensioners under the Sustaining Progress national agreement.
In July, the Labour Court recommended payment but only if workers agree to productivity changes.
The CWU then proposed a number of amendments but an Post had disputed the cost of these work practice changes, with its estimates ranging from €20 million to €34 million.
In its statement, the NIB said it believed the clarification of the cost and implications of these amendments was essential if the dispute was to be resolved.
The team of accountants appointed by the NIB to examine the costs will report back by November 14th.
An Post said it was relieved at the outcome of the talks. "However, we have concerns about the effect on services tomorrow, given the union's indication that they're not going to be able to call off the action at this stage," said spokeswoman Anna McHugh.
She said it appeared there would be some disruption to services tomorrow. "But we'll be in touch with the CWU over the evening in an effort to minimise the impact on customers tomorrow."
An Post has told customers it will not be possible to guarantee any mail services in or out of the country due to the planned strike.