SIPTU will reveal the result of a ballot later today which could see 10,000 hospital support staff engage in strike action.
Staff are threatening to go on strike unless they get access to a job evaluation scheme.
SIPTU says it will help people like porters, cleaners and security staff to be paid appropriately for the amount of work they do.
If the action goes ahead it will start on March 7, the same day that 30,000 nurses begin a work-to-rule, a move which may lead to hospital bed closures and cuts to hospital services.
After voting earlier in the month to begin action from that date on, INMO members will no longer work overtime, will not cross-cover for other absent staff and will not redeploy to other parts of their hospitals.
If that dispute remains unresolved, the planned action will escalate a week later to involve rolling work stoppages in hospitals and community services.
Meanwhile SIPTU is also warning that industrial action could be on the way for Dublin Bus and Irish Rail, as well as Bus Éireann.
The union is balloting members in Dublin Bus over a broken settlement deal, it’s also in discussion with members of Irish Rail over broken agreements, and members in both companies have already pledged solidarity with their colleagues in Bus Éireann who are striking on February 20 over threatened cuts.
SIPTU Sector Organiser, Willie Noone, says if all three companies are ignoring their own agreements, they leave workers with no option but to take a stand.