Patients in the health service face potential disruption to services by Christmas after the Irish Nurses and Midwives Organisation decided to ballot for strike action over pay and staff shortages.
If members vote in favour, nurses across the public service will hold a 24-hour stoppage with only emergency cover provided.
The number of 24-hour strikes would increase progressively if the dispute remained unresolved.
The INMO will not commence its ballot for two weeks to give the HSE and the Department of Health a "cooling-off" period to bring forward "meaningful" proposals.
The HSE and the union are due to meet before the end of this week.
The INMO argues that only a 12% across the board pay rise (bringing them into line with other grades like physiotherapists and occupational therapists) will make nursing sufficiently attractive to address staff recruitment and retention problems.
However, the Public Service Pay Commission ruled out a general pay rise, opting instead for a €20 million package of allowances targeted at the areas with the most severe shortages.
That package would only benefit around half of INMO members, and was rejected by 94% of them.
The INMO cited HSE figures showing that for every four nursing vacancies, there is only one application.
It noted that there are now 2,600 fewer nurses working in the public health service today compared to 2007 - adding that the number of staff nurses had fallen by 227 between December 2017 and September 2018.
They also claimed that the HSE pays recruitment agencies a "bounty" of €10,000 for every nurse or midwife they find to hire.
INMO General Secretary Phil Ní Sheaghdha expressed the hope that during the two week cooling off period before the ballot commences, the management side would bring forward meaningful proposals to avert a dispute.
Asked whether patients could face industrial action before Christmas, she said that was neither ruled in nor out.
Asked about the impact on patients, she said the focus was always on the safety and quality of patient care, which would benefit from any settlement.
Ms Ní Sheghdha said that at the moment nurses are embarrassed by the level of service they are forced to provide to patients.
She said the INMO was not in dispute or in breach of the Public Service Stability Agreement, and rejected the suggestion that a Government concession to the nurses and midwives would trigger knock-on claims across the public service
A spokeswoman for the Minister for Health Simon Harris said he was pleased that engagement is due to take place between the unions representing nurses and the HSE this week.
She said the Minister was hopeful that all sides will engage constructively to prevent industrial action from taking place.