Bus Éireann has said its current financial position is giving serious cause for concern and said it has seen unprecedented levels of absenteeism this year.
In a letter to unions, the company says revenue on a number of services is down considerably on previous years and its operation is under threat on a number of fronts.
It cites the loss of a number of routes in the greater Dublin region.
In the correspondence, Bus Éireann has invited unions to talks later this month to discuss possible pay increases.
The company says it is very difficult to see how it could afford to meet the pay claim unions have asked for, but says it is prepared to examine the matter.
It comes after the company announced that it is beginning a campaign to recruit almost 200 staff, including 190 driver positions and additional mechanic jobs.
The company says the new staff are required for an expansion and enhancement of services on a number of its routes across the country that will be introduced over the next four to six months.
The service enhancements are planned for regional city networks, town services and several Expressway intercity routes.
The new roles will be required in Dublin, Cork, Galway, Mayo, Waterford, Wicklow, Navan, Drogheda, Limerick and west Clare.
Bus Éireann CEO Ray Hernan said the majority of the service expansion will be delivered on Public Service Obligation routes and when introduced the expansion "should incentivise more people to make the switch to public transport".
He added: "Much change and progress has been delivered across Bus Éireann and Expressway, since the acceptance of a new Labour Court Agreement by staff last year.
"We are continuing to transform our business to deliver an enhanced experience for our customers."
A Bus Éireann spokesperson has said while the company is still "technically insolvent" and financially fragile, it is trying to grow the company and return to sustainability by recruiting for the new posts.
Nicola Cooke said a lot had "been achieved with the help of staff to deliver critical efficiencies".
SIPTU’s Greg Ennis said that as long as underfunding remained an issue in the public transport sector, industrial relations difficulties would intermittently arise in companies such as Bus Éireann.
A spokesman for the National Bus and Rail Union said: "The good news around the announcement on recruitment should now be matched with a long overdue pay rise for Bus Éireann staff.
"The NBRU would expect that the response to our claim will (in the context of this current recruitment drive), be met with a similar eagerness from the company to that which is accompanying this latest announcement.
"Failure to so do will result in an inevitable spiral towards unnecessary industrial action."
However, Ms Cooke said the company would discuss a claim for pay increases with unions separately, but for now it was focused on long-term sustainability and growth.
She said it needed to return to profitability before committing to any pay increases for existing staff.
Greg Ennis of SIPTU advised that as long as underfunding remained an issue in Irish public transport, industrial relations difficulties would intermittently arise in companies such as Bus Éireann.