The head of the Labour Relations Commission (LRC), Kieran Mulvey, has admitted his officials are in a race against time to secure a breakthrough in the ongoing bus dispute.
Talks at the LRC were scheduled to resume today as unions press for "cast-iron guarantees" over issues such as employment and the future of bus routes.
But the threat of strike action this weekend remains in place - and would cause further chaos for passengers.
The decision by bus workers to down tools over the May bank holiday weekend cost hundreds of thousands of euro in lost revenue.
But sources involved in the negotiations have admitted that securing agreement this week will prove difficult given the range of different stakeholders involved.
The dispute centres around plans by the National Transport Authority to put 10pc of bus routes out for private tender.
These proposals could see several Dublin Bus routes, as well as Bus Éireann services from Dublin to Tullamore, Portlaoise and Kildare, taken over by private companies. The plans also propose the tendering of routes in Waterford city.
The Government has said the measures will result in improved services and ultimately save the taxpayer money.
However, the unions insist the move will open the door for a campaign of privatisation.
They also claim the measures will put jobs at risk and result in a deterioration of their members' conditions.
Unions will today demand guarantees surrounding the future employment of Bus Éireann and Dublin Bus workers if these plans go ahead.
A major sticking point in the talks also surrounds the prospect of further privatisation after 2019, when current Bus Éireann and Dublin Bus contracts expire.
Unions are fearful that if the two State companies lose out on these contracts in 2019, the terms of conditions of workers will deteriorate.
It's understood that the LRC may propose to ringfence this particular issue for separate negotiations involving NTA and Government officials.
The National Bus and Railway Union has already threatened legal action over privatisation plans.
Speaking to the Irish Independent last night, LRC chief Mr Mulvey said the initial talks were "positive" and "fruitful".
But he admitted it will prove difficult to secure a breakthrough ahead of Friday, when the next phase of strike action is scheduled to take place.
"Certainly time is against us … it is fair to say our initial objective is ensuring no more strike action takes place," Mr Mulvey said.
The National Bus and Railworkers' Union said its focus is also on trying to ensure the strike does not go ahead.
"But it's important to recognise that we don't have sole control over that happening. That is up to all the parties playing their role, including the department and the NTA," said NBRU general secretary Dermot O'Leary.
Mr O'Leary added that all parties now have a clear idea of each other's position.
Business groups are closely watching the outcome of the talks amid fears of the impact further strike action will have on trade.
Bus Éireann has said it intends to "engage constructively" in the orders to "try and avoid any further disruption of our services".
A spokeswoman for Transport Minister Paschal Donohoe said the Government is not directly involved in the talks but is available to provide assistance if required.
The talks at the LRC were instigated by Mr Donohoe in a bid to allay fears of drivers at both Dublin Bus and Bus Éireann.
They are due to continue until Thursday.