Talks between Luas drivers and management have ended at the Workplace Relations Commission without agreement.
SIPTU, which represents drivers, said the two 48-hour stoppages planned for next month would now go ahead as scheduled.
The Luas operator Transdev also attended the talks.
The sides met for almost four hours today in the dispute over pay at the company. There are no plans for further talks.
The WRC has asked both sides to reflect on their position.