SIPTU's divisional organiser Owen Reidy has said no decision has been taken on whether a ballot will be held for an all-out Luas strike, although it was discussed at a meeting of drivers today.
Mr Reidy's comments contradict those of shop steward Richard McCarthy, who said they would ballot in the next two weeks.
Mr Reidy also said the Labour Court would next week be exploring whether there was the scope for an intervention in the dispute and would talk separately to the Irish Congress of Trade Unions and Luas operator Transdev Ireland.
Speaking after the meeting earlier today, Mr McCarthy said drivers felt they had to have a defence against attacks by Transdev, including the suspension of the sick pay scheme and cancelling some annual leave.
The company has said they are awaiting official correspondence from SIPTU and will not be making any further comment tonight.
SIPTU to hold ballot for all out strike action on Luas. They say they are still open to WRC intervention. https://t.co/oawLFLFxS4— RTÉ News (@rtenews) May 20, 2016
There are no Luas services today as drivers stage their 12th day of strike action in their dispute with Transdev.
Transdev had urged drivers to call off today's action, warning that it will not conclude a pay deal in excess of the 13% agreement already reached with non-driver grades.
Transdev Ireland Managing Director Gerry Madden warned that if the dispute continued, the company would take what he called "other lawful means" to bring it to an end.
Limited services on Red Line from tomorrow
Meanwhile, the Luas Red line from Jervis to the Point will close tomorrow night for two months.
The closure from 9pm until the end of July is to allow works related to the new Luas Cross City expansion.
A temporary bus service for Luas customers to cover the closed stops will be put in place.
The stops affected are: Abbey Street, Busáras, Connolly, George's Dock, Mayor Square - NCI, Spencer Dock and The Point.