An Post is to begin sealing postboxes in Dublin over the next few days, so that people cannot post letters, if the row affecting postal services continues to escalate.
The company suspended more than 100 workers at its Dublin Mail Centre yesterday, taking to 420 the number removed from the payroll since the dispute began at the weekend.
It is still asking customers not to post mail to or from Dublin as well as parts of Wicklow, Monaghan, Louth, Meath and Galway.
About a third of the normal number of deliveries were made to most of the affected areas yesterday, but a company spokesman said the service was likely to "wind down" in the coming days.
An escalation of the dispute to other parts of the State was averted for the time being, however, when the Communications Workers' Union decided to delay implementing a national strike.
Members had already voted by a six-to-one majority for the strike, before the dispute at the weekend at the Dublin Mail Centre.
An Post began suspending staff at the centre late on Friday night, claiming they were refusing to carry out normal duties.
However, the CWU claims the company was attempting to introduce new sorting arrangements, which have implications for sorters in local offices, without agreement.
The Minister for Communications, Mr Dermot Ahern, urged the two sides to use the State's industrial relations machinery to try to resolve the dispute.
"Neither the country nor the company can afford a dispute at this time. The company is facing continuing losses in recent years which will amount to almost €100 million," he said. "Obviously these continuing losses are not sustainable." However, it is understood Mr Ahern has no immediate plans to intervene in the dispute.
The Taoiseach, Mr Ahern, also warned last night that the country could not afford a prolonged dispute.
Informal contacts were made with both sides by the Labour Relations Commission yesterday with a view to finding a basis for talks.
The atmosphere between the two appeared to worsen yesterday. Mr Sean McDonagh of the CWU said it was time for An Post "to come to its senses" and accused the company of "running the postal service down".
Mr Larry Donald, director of corporate and regulatory affairs with An Post, said the union's actions were designed to "harass" the company into the 3 per cent increase due to staff under the Sustaining Progress agreement. Having lost more than €40 million last year it could not afford to do so, he said.
Utility services and other businesses were considering contingency arrangements for billing their customers. The Department of Social and Family Affairs said it had introduced special arrangements for payments by cheque during the dispute.