There has been a possible breakthrough in the Luas dispute as the Workplace Relations Commission has invited both Luas operator Transdev and the drivers to talks tomorrow.
The WRC has urged the company not to hire private buses to replace trams during a strike planned for St Patrick's Day.
In a statement, the WRC said: "In order to create a climate of positivity to these engagements and without prejudice to the position of any party, the commission has requested the company to defer any alternative travel arrangements for Luas passengers on Thursday St Patrick's Day."
It is hoped the re-engagement with the drivers may stave off the strikes due to take place on seven days in March and April, including St Patrick's Day.
Transdev MD Gerry Madden this evening said: "Transdev is in resolution mode and is happy to go to talks tomorrow in the WRC and engage in meaningful discussions."
Transdev added that it will not operate buses on Thursday.
SIPTU Divisional Organiser Owen Reidy welcomed the fact that Transdev had stepped back from the hiring of private buses.
He also welcomed the invitation from the WRC, saying it created space to seek a resolution.
However he stressed that a lot of work remained to be done.
Meanwhile, the three non-driver grades at the Luas have adjourned their negotiations at the WRC with some progress reported.
They will resume in the morning.
Transdev earlier denied that it was engaging in strike-breaking by hiring private buses to operate along Luas routes during the planned strike on Thursday.
Mr Madden said the Luas had already had four days of strikes, and strike number five is approaching.
If he was in the business of strike-breaking activity, he said, he could have done that before now.
He said the difference with this strike was that it is a public holiday for children and families.
He expressed surprise that people were surprised that he was trying to do something to help that along.
SIPTU this afternoon warned that the St Patrick's Day strike was unlikely to be called off.
Assistant organiser John Murphy said the drivers had been excluded from talks - and unless that changed in the next 24 to 48 hours, the strike was set to go ahead.
He said it was ironic that the company had said through the WRC that it was not prepared to engage with the drivers, yet had consistently said that no resolution can be achieved without all grades agreeing.
He said it was a bit like trying to ride both horses at the same time - and neither will get to the finish line.
He said the drivers remained available for talks and that last week, all four grades had called off the strike scheduled for 8 March, but that goodwill gesture had been thrown back in the drivers' faces in less than a day.
Iarnród Éireann also meeting unions at WRC
Meanwhile, Iarnród Éireann management and unions have also been holding talks at the WRC in a bid to resolve a dispute over proposals for a more-frequent, ten-minute DART service.
The expanded service, up from every 15 minutes currently, will mean more trains for customers and more jobs for drivers.
An extra 1.6 million passenger journeys were made by DART in 2015 - a growth of over 10%.
The company argues that the new schedule can be introduced within existing resources as it has trained up 17 additional drivers.
However, SIPTU and the National Bus and Rail Union insist that the move involves additional productivity.
The unions have already balloted for strike action in the event that the company moved to introduce the new timetable on 10 April without agreement.
The company's Director of Human Resources Ciaran Masterson said they were trying to agree rosters with the existing complement of staff to allow them to grow the DART service over the coming years.
He rejected union claims that the introduction of the new service was a productivity issue which should be dealt with in an ongoing Labour Court process.
However, NBRU General Secretary Dermot O'Leary said that as far as his union is concerned, the ten-minute DART schedule is a productivity measure.
He said that once the company accepted that it was a productivity issue, then they could discuss compensation.
He acknowledged that workers in all three CIE group transport companies, who had been waiting years for a pay rise, were watching the Luas dispute closely - and were determined to get an increase this year, whatever happened in the transport sector.
SIPTU Assistant Organiser Paul Cullen said they were going to ask the company to take a step back - and withdraw the new timetable until such time as a Labour Court recommended investigation of productivity issues was completed.
However, he warned that if the company insisted on introducing the ten-minute DART service without agreement, there will be a dispute.
He also confirmed that SIPTU has written to Iarnród Éireann confirming that it will be serving a "substantial" pay claim on the company this year, as its members received no increase since 2008.
Talks have now adjourned until tomorrow.
Sources said one option under consideration is an interim solution - but much work remains to be done.