Rolling work stoppages by striking nurses will target hospitals in Dublin and Tipperary on Wednesday.
The Irish Nurses Organisation (INO) and Psychiatric Nurses Association (PNA) today announced one-hour demonstrations between 11am and midday at St Vincent's Hospital in the capital as well as South Tipperary General Hospital, Clonmel and South Tipperary Mental Health Services.
All essential or emergency nursing services will be maintained but planned operations will be disrupted during the strike period.
Both unions stressed that the escalation will go ahead in the absence of further negotiations over their demands on pay and conditions.
A second series of stoppages planned for Friday will be announced on Wednesday. INO general secretary Liam Doran said: "This is the latest phase of our campaign, which received a 98 per cent endorsement from our members and it is being designed, through its duration, to minimise the disruption to patients."
PNA spokesman Seamus Murphy said: "Our preference is to be negotiating how to make progress on these issues.
"However the resolve of our members remains absolute, and the threats and innuendo coming from the management side are only serving to undermine the long-term relationship which will exist between our members and senior managers in the health service.
HSE
"It should be recalled that all of these senior managers, only two years ago, also took industrial action in the form of a nationwide work to rule in pursuance of their interests".
Nurses have vowed to move from a work to rule stance to strike action this week in their campaign for a 10 per cent pay rise and a 35-hour working week.
Despite pleas from the Health Service Executive (HSE) and hospital consultants for the industrial action to end, the unions' 40,000 nurses said they are committed to the campaign.
But both Taoiseach Bertie Ahern and the Minister for Health Mary Harney insisted they must wait until the public service benchmarking process begins later in the year for their pay claims to be assessed.
The strike action began at 8am last Monday after three weeks of negotiations between health chiefs and unions collapsed during crunch talks at Government buildings.
Nurses are demanding a 10 per cent pay rise but the Government insists a wage hike would be outside the terms of an existing national agreement on public sector pay.
Seamus Murphy, PNA
There was agreement in principle between all sides on the introduction of another key demand - a 35-hour working week - but the HSE refused to identify a starting date for the new hours.
The HSE said it was "willing to engage" with the nursing unions to seek a way through the "current impasse".
"The HSE's overriding concern is patient care and reducing the anxiety being experienced by families. The HSE has accepted the Labour Court recommendation and is willing to resume discussions on this basis," a statement said.
It added that while the issue of a reduced working week is complex, progress had been made through the National Implementation Body and that further analysis is needed.
The HSE reiterated the Minister for Health's view that benchmarking is the vehicle that must be used to address disputed pay relativities in the public sector.
It said the Government policy on pay is very clear and benchmarking is the vehicle to address disputed pay relativities in the public sector.