Luas workers are to escalate their industrial action over pay by holding two further strikes on 8 March and St Patrick's Day.
The staff, who are represented by SIPTU, went on strike last Thursday and Friday causing major disruption to around 90,000 customers.
They are set to strike again this Thursday and Friday.
Luas employees are seeking pay rises ranging from 8% to 53% but their employer Transdev, which operates the Luas service, has described the claims as unsustainable and unaffordable.
Management and SIPTU are deadlocked, and so far there is no indication of any intervention by either the Workplace Relations Commission or the Labour Court to get them back into talks - as it is felt the two sides are too far apart at this point to make progress.
The strikes have already had a significant cost for both sides. Because they proceeded with industrial action, workers have lost their annual bonus worth 6.5% of salary.
In addition, by the end of this week, they will have four days' pay cut - equivalent to almost a 2% pay cut.
That cost will rise further if the strikes on 8 and 17 March go ahead.
The company is already facing fines of €100,000 for each day when it fails to provide a transport service.
However, it will save money by not paying wages and the annual 6.5% bonus.
The real cost will be to the 90,000 customers a day who will have to make alternative arrangements - with the added problem of the disruption to tourists and businesses in Dublin for the St Patrick's Day festivities.
Minister for Transport, Tourism and Sport, Paschal Donohoe, has this evening said the announcement of further strike action by Luas workers is extremely disappointing.
"News that Luas workers are to stage a further two days' strike action on 8 March and again on St Patrick's Day will come as exceptionally bad news not only to commuters, who rely on Luas for their daily commute, but also to the 100,000 overseas visitors who will travel to Dublin to help us celebrate our national holiday.
"It appears the decision to stage a further two days of strike action, in particular on St Patrick's Day, is being taken with a view to causing maximum disruption, which will be welcomed by no one.
"Our economy is growing but is still fragile. This industrial action puts added pressure on businesses who are attempting to secure a more stable footing for the future and on our job creation ambitions," added Mr Donohoe.
Transdev Managing Director Gerry Madden said: "I am shocked and disappointed to learn that Luas employees plan on stopping the service not just this week, Thursday and Friday, February 18 and 19, on Tuesday March 8 and St Patrick's Day - March 17."
"Not only are SIPTU threatening the company and Luas customers but they will seriously impact business and the tourist sector by their actions," he said.
"Their claims are unjustified. They are not benchmarked with any other sector.
"They will damage the Irish economy, businesses and the good reputation of Luas. Their action will impact on the thousands of families who use Luas to travel into and out of the parade, not just the parade but all the events in the city associated with the festival," Mr Madden added.
Mr Madden reiterated that Transdev was prepared to discuss pay increases in excess of the consumer price index of between 1% and 3%.
He said the SIPTU claim on pay alone would add €6m per year - or €30m over five years - to the cost of operating the Luas.
He urged the Luas staff to re-enter talks at the Workplace Relations Commission to resolve the dispute.