Irish Rail has said it is "ridiculous" that industrial action is being proposed across its network.
The company said the action made no sense when the company was willing to sit down to negotiate with workers on their concerns.
Siptu and the National Bus and Rail Workers Union are to come up with a plan on Thursday for the action, which has been backed overwhelmingly by members, with 92% of Siptu members in favour in the dispute over productivity measures.
Company spokesman Barry Kenny (pictured) said the company was in a difficult position, as it was losing more than €1m a month.
"We cannot (ask for) more money to address issues, many of which have been addressed by the Labour Court and rejected," he said.
"Having industrial action is just ridiculous where we have a situation where we are committing to our employees and drivers that we can boost their earnings if we can identify productivity measures where we can split the benefit."
Update 9am:Meanwhile, unions have hit out at the company's refusal to discuss past productivity measures, which they say led to a breakdown in discussions.
Siptu spokesperson Paul Cullen refused to be drawn this morning on speculation that the industrial action is most likely to affect trains scheduled over the October Bank Holiday weekend.
He said: "I have no definitive dates…but action is likely over the coming weeks, rather than months. It is expected that it will affect all intercity services and all commuter services."