A special meeting of the board of the Conwy and Denbighshire Trust is being recommended to back the merger with the Wrexham-based North East Wales Trust.
Geoff Edkins, regional organiser of Unison, who was spokesman for the joint trade unions and staff organisations, said they recognised that for most staff the changes would not happen on merger day and that the process would take some years.
He said: "Staff are not just worried about whether they will have a job, they are also worried about where that job will be, who will manage them and with whom they will work.
"We are yet to be convinced that the merger of the trusts will produce benefits to patients or staff."
Consultation revealed potential disruption of effective clinical teams, increased travel time for patients and clinicians and more remote directorate staff as some of the disadvantages of a merger.
The negotiating committee would prefer to see all three North Wales trusts merged, a view also held by the Conwy Federation of Community Health Councils, which is the patients' watchdog.
The Federation says that if the Minister refuses to merge all three trusts, then Llandudno Hospital should be transferred to the North East-Conwy and Denbighshire Trust.
The Royal College of Nursing has highlighted several concerns and sought assurances in a letter to Gren Kershaw, chief executive of the Conwy and Denbighshire Trust.
The RCN's lead steward Terry Kirton asked why the public had not been consulted and whether the £300m redevelopment of Ysbyty Glan Clwyd would go ahead.
Mr Kershaw replied that as the merger concerned changes in management and organisational structure rather than any specific proposals for service change the Minister had determined that consultation would be with the CHCs, unions and staff.