Unions representing Bus Éireann drivers say we should expect strike action sooner rather than later.
They are set to meet with management at the Workplace Relations Commission today.
It is expected that the State-owned company will announce restructuring plans at the talks, while unions will lodge a pay claim.
The NBRU's Dermot O'Leary is warning that strike action is likely.
Mr O'Leary said: "If the reaction is negative to our claim or if the announcement on Expressway is forthcoming as has been reported, then obviously we will move to ballot our members immediately with a view to having industrial action sooner rather than later."
Management at Bus Éireann are expected to propose significant changes and restructuring at its loss-making Expressway inter-regional coach services, which is facing increasing competition from private operators.