SIPTU members in Dublin Bus and Irish Rail are to ballot for industrial action in support of Bus Eireann workers.
It comes as the all-out strike continues for a fourth day.
Today the Board of Bus Éireann urged all employees to urgently engage with management to agree a survival plan to prevent insolvency.
The call followed a meeting at which the board considered a management plan to secure the future of the company, which includes cost efficiencies to eliminate what Bus Éireann calls "grossly inefficient work practices".
