Health sector unions and the Haddington Road Agreement Oversight Group are holding discussions on a row over how additional unpaid hours are worked.
This is the first significant dispute relating to the implementation of the HRA.
In the original agreement, staff were to work additional unpaid hours that varied depending on their grade or job.
The Health Service Executive argued that this was necessary to reduce the bill for hiring costly agency staff.
However, there was a provision permitting some staff to retain their existing hours and take a proportionate pay cut.
The HSE announced last month that it was terminating the opt-out and that all staff would have to work extra hours in accordance with the HRA.
Unions are resisting the elimination of the opt-out provision.
Other issues that may feature include the HSE Service Plan provision seeking additional unspecified pay savings of €108m in 2014.
Unions have already stated categorically that they will refuse to concede any payroll reductions beyond what is already stated in the Haddington Road Agreement.
A planned redundancy scheme for the health sector may also be on the agenda.