It's feared Dublin Bus and Irish Rail services could face disruption tomorrow, as the Bus Eireann strike continues.
A protest is being planned for outside the Dail, to coincide with the Transport Minister's appearance at an Oireachtas Committee meeting to talk about the dispute.
Industry Correspondent with the Irish Times Martin Wall said: "Some Dublin Bus and Irish Rail staff will stop work for a period tomorrow to attend that protest. Any such action would be unofficial and we'd have to wait and see how extensive it is.
He added: "There certainly does appear to be a prospect of work stoppages in the other CIE companies tomorrow for a period at least. "
This may not be the only threat to services, SIPTU has said Dublin Bus and Irish Rail staff will be ballotted on whether or not to down tools in support of their CIE colleagues.
Bus Eireann staff walked off the job four days ago in a row over cost-saving measures.
The company says the measures are needed to save it from going bust.