Talks are to resume today over pay restoration for Section 39 organisations.
The voluntary groups provide social services and healthcare on behalf of the HSE by way of service level agreements.
SIPTU, the Department of Health and the HSE are due to meet later at the Workplace Relations Commission.
SIPTU are seeking pay restoration for Section 39 workers and says this must start in the final quarter of 2018.
The union's Paul Bell says if that does not happen, there could be strike action.
He said: "There are 10 Labour Court recommendations at this stage, confirming our member's rights to pay restoration and confirming that they have pay links to the public sector.
Explaining the difficulties of resolving this dispute Ball said: "The issue that we have now is that our members are so far behind, they are owed payments from April 1, 2017, owed payments also from January 1, 2018, and there is a payment now due again in October 2018.
"At this stage, it is very very difficult to see what ground can be agreed upon whereby pay can be restored."
- Digital Desk