The National Bus and Rail Union has warned members at Bus Éireann to prepare for "the mother of all public transport disputes".
Staff at the bus company are due to commence an all-out indefinite strike on Monday in a row over the company's unilateral implementation of cost-cutting measures which unions argue could reduce take-home pay by up to 30%.
However, management argues that cost savings totalling €30 million are essential to halt mounting losses at the company which could be insolvent by May without drastic action.
Behind the scenes efforts are continuing in a bid to find a basis to bring the two sides to the negotiating table at the Workplace Relations Commission, but so far there is no sign of a breakthrough that would enable further talks.
In today’s statement, NBRU General Secretary Dermot O'Leary warned that the timeframe for securing a resolution is fast approaching the point of no return - adding that the complexities of the dispute make it "extremely difficult if not nigh on impossible" to achieve a resolution between now and midnight on Sunday.
He said unions had publicly declared that they were prepared to engage on an efficiency/work practice agenda as a building block towards an overall solution - including playing their part in resolving the €9m crisis at the loss-making Expressway operation.
However, he accused the company of being determined to make a solution unattainable, by imposing financial sanctions without agreement, and setting the bar too high in terms of what they are seeking to achieve.
He claimed the company was geared towards maintaining its "race to the bottom agenda" in targeting savings of €30m - which was not a space in which the union was prepared to engage.
He said the most recent letter from the company had referred to a further restructuring plan that would not be completed until the end of March at the earliest.
He said members would absolutely not entertain the notion of buying a "pig in a poke", having previously been burnt by accepting two cost-cutting plans in the last seven years to place the company on a sound footing.
SIPTU Divisional Organiser Greg Ennis also referred to the March restructuring plan, saying unions could not negotiate in the dark, without full knowledge of what was coming down the tracks in the end-of-March restructuring plan.