Preseli Pembrokeshire AM Paul Davies is fighting to ensure that any new hospital in Ceredigion is built in Cardigan, not elsewhere.
Planning issues have held up the building of a new hospital in Cardigan and sites in Lampeter and Felinfach have been put forward as alternatives.
"It is crucial for my constituents that this facility is located in the Cardigan area," he told the Senedd.
"Access to a facility in Lampeter or Felinfach would be unacceptable to my constituents in north Pembrokeshire."
He won an assurance from Mrs Hart that she also wanted the new unit to be built in Cardigan.