Management and unions in Irish Ferries were last night locked in detailed negotiations aimed at resolving the bitter dispute at the company.
Issues such as pay rates and working hours for proposed new agency crews were being discussed by management and Siptu representatives at the Labour Relations Commission.
The late-night talks were being held as a deadline for agreement set by the company loomed.
It had threatened to withdraw a substantial proportion of a redundancy package on offer to existing crews if its three Irish Sea vessels were not immediately returned to service.
The ships have not sailed for almost three weeks because of the dispute over the company's proposal to replace unionised seafarers with cheaper agency crews from abroad.
Two of the ships, the Isle of Inishmore and the Ulysses, were scheduled to sail from Pembroke and Holyhead respectively at 3am today. A company source indicated that this, in effect, was the deadline for agreement.
A union source at the talks said progress was being made, but the prospects of a deal remained in the balance.
The Seamen's Union of Ireland, which represents about 60 per cent of seafarers at the company, was also in attendance at the talks.
General secretary Robert Carrick said members were "up in arms" at the prospect of having redundancy payments cut by 25 per cent or more. One member, for example, stood to lose half of a €190,000 severance payment.
Mr Carrick claimed the company's move to cut redundancies could backfire, in that many of those who had applied to leave would now choose to keep their jobs.