Behind-the-scenes efforts will continue today to resolve a dispute which led to Irish Ferries withdrawing three of its four vessels from service yesterday.
The company also plans to temporarily lay off 600 staff without pay on Friday because of the failure of unions to negotiate cost-cutting proposals.
One union reacted to yesterday's move with a threat to disrupt the company's one remaining service, operated by the MV Ulysses between Dublin and Holyhead.
The company is seeking to make 52 staff redundant as part of a drive to achieve savings of €3.4 million a year.
Negotiations have not taken place however, because of a refusal by the Seamen's Union of Ireland to participate in joint negotiations with the other union involved, SIPTU.
The Irish Congress of Trade Unions wrote to the SUI yesterday urging it to accept a Labour Court recommendation that it take part in joint discussions.
Further contacts between ICTU and the union are expected to be made today.
However, Mr Robert Carrick, the SUI general secretary, said the union had never sat down with SIPTU in talks with Irish Ferries.
"I don't see what's wrong with continuing as we have in the past."
His union had begun a ballot on industrial action in the event of the lay-offs going ahead on Friday.
If the vote is in favour of action, the MV Ulysses service could be disrupted by the end of next week.
Although Irish Ferries had warned that vessels would be taken out of service, its decision to do so as early as yesterday was not expected.
Mr Carrick claimed that 300 passengers and 90 freight units were left stranded at Rosslare yesterday as a result of the move.This was denied by the company, which said all of those affected had been accommodated on alternative services.
Mr Jimmy Quinn of the Irish Road Haulage Association, which called yesterday for the two sides to resolve the dispute, said it had received no reports of anyone being left without a means of travel.
However, he said there was not much spare capacity on Irish Sea ferry services, and difficulties could arise at the weekend if the dispute was not resolved.
Mr Pat Delaney of the Small Firms Association said there was a "clear and present danger" to small exporters if the dispute escalated.
SIPTU, which is prepared to negotiate with the SUI, says its members will continue to work on the MV Ulysses, even if lay-offs take place at the weekend.
A company spokesman said 1,300 people were booked to travel on the three vessels taken out of service yesterday. All passengers were being offered their money back, or the option of travelling on the Ulysses or a competitor's service.
In a statement, the company said its cost base was more than 30 per cent out of line with that of its main competitor, and it had been attempting to address the situation since mid-2003.
It regretted having to withdraw the three vessels from service, but had timed the move to cause the minimum possible degree of disruption to passengers and freight customers.