The board of Bus Éireann has said it is "gravely concerned" about losses the company is experiencing while strike action is being carried out by its staff.
An indefinite strike action, which began due to a dispute over management's decision to implement a survival plan for the State-owned company without union agreement, is under way.
Bus Éireann has said the losses are accelerating, and estimated that the dispute is costing it €500,000 per day.
Around 110,000 Bus Éireann customers are affected by the strike.
The board of Bus Éireann met to consider management proposals for a survival plan including up to 300 redundancies.
Following the meeting, the company said in a statement that it was unable to sign off on the 2016 company accounts, or pass this year's budget without agreement from its staff.
It said its inability to sign off the accounts is a "very serious matter", and it "must now formally advise CIE that this governance requirement will not be met".
Management presented the board with a plan to secure the company's future - the key component is elimination of "grossly inefficient work practices".
It has requested all staff to urgently engage with management at the company through their representatives to agree a survival plan to prevent insolvency.
The company said without a plan encompassing necessary work practice changes to generate savings, it cannot fund a voluntary redundancy scheme.
The company also said without a plan generating savings to fund voluntary redundancies, the board has no option but to consider other measures to avoid insolvency.
Bus Éireann's Chief Commercial Officer has said the company is perfectly salvageable.
Speaking on RTÉ's Drivetime, Stephen Kent said measures can be taken to avoid immediate insolvency.
He said based on delivering a survival plan that would ensure the long-term viability of the company, there would be 300 voluntary redundancies.
Mr Kent said, however, that the redundancies would have to be targeted.
He said management is prepared to go to any forum for talks with unions, but discussions would have to be time-limited.
Asked about the potential spread of the industrial dispute to Iarnród Éireann or Dublin Bus, Mr Kent said: "There is absolutely no reason for that to happen. There is no dispute with each of those two companies."
He said there is an issue with the Minister for Transport getting involved in the dispute, saying it is a problem that can be solved between management and staff representatives.
"This is all a perfectly salvageable business. What we need to is engage with the employees and to get people to accept what we believe are very reasonable changes to some custom and practice."
"And we require some flexibility in the driver rosters, and some of the other aspects of the business, in order to make the business more flexible and more responsive. And it will generate the savings", he added.
Disruption may spread to other transport companies
Earlier, Bus Éireann unions stressed that they were not in dispute with other CIE group companies but said they could not rule out workers at Dublin Bus and Iarnród Éireann joining the protest.
This afternoon, SIPTU confirmed that its members in Dublin Bus and Iarnród Éireann are to ballot for industrial action in light of the ongoing Bus Éireann dispute.
SIPTU representatives from the three companies met at Liberty Hall in Dublin to discuss the ongoing strike.
The meeting heard of a planned protest in support of Bus Éireann workers to be held at Leinster House on Wednesday to coincide with a meeting of the Oireachtas Transport Committee, which Minister for Transport Shane Ross is expected to attend.
SIPTU sector organiser Willie Noone said: "The representatives agreed that the protest should be supported as it is a means of highlighting the failure of the minister to take responsibility for the dysfunctional state of the public transport service.
"We are encouraging members of the public and of the union, including those who work in the public transport sector and are available, to attend the protest.
"The meeting also gave a mandate for a ballot for industrial action of union members in Dublin Bus and Irish Rail in sympathy with and in support of their colleagues in Bus Éireann.
"They believe that they are next in the firing line if management in Bus Éireann is allowed to force through cuts to wages and changes to conditions of employment of their staff."
Mr Ross's department issued a statement today noting his "extreme concern" over the ongoing situation.
"The minister remains extremely concerned about the impact of the Bus Éireann strike on the travelling public," the statement said.
"The strike is also harmful to the company's already difficult financial position. Realistic negotiations are required, the type that will lead to an agreement that improves the company's operations and efficiency and restores the company to a sustainable future.
"The State's industrial relations institutions are available to assist the two sides in reaching a fair and sustainable agreement."
The National Bus and Rail Union has again called on Mr Ross to establish a forum for talks.
General Secretary Dermot O'Leary accused management of continuing to wreck the national transport system by continuing to insist on a race to the bottom to establish a yellow pack bus company.
He claimed a solution to the current Expressway crisis could be arrived at through talks centred on what he called the "already mooted efficiency based agenda".
However, the company has previously accused unions of failing to engage meaningfully on issues like cuts to unnecessary overtime.
As of now, there is no indication of any intervention by the Workplace Relations Commission or the Labour Court to bring both sides to the negotiating table.
Train services returned to normal at the weekend and Iarnród Éireann said all its services operated on all routes today.
"We do not anticipate further disruption arising from the Bus Éireann dispute at this time. Iarnród Éireann is not a party to this dispute."
It also said higher demand is expected on its services and advised those customers with flexibility to travel outside peak times.