The ferry terminal in Fishguard could close for up to 3 months according to its operator, Stena Line.
The closure would allow for the replacement of mechanised bridge which connects the ferries with the dock in a GBP 5 million project. The most likely period is from February 2019.
Stena Line revealed it was "committed to examining the possibilities of investing in key elements of the port infrastructure".
The cruise company is looking at replacing Linkspan provision, a key ship-to-shore connection which allows vehicles to board or disembark at different tide heights.
Stena Line lodged initial outline planning application to the County Council of Pembrokeshire, and its statement said the port would close for approx 3 months, but that was yet to be confirmed.
The terminal's closure could include the route's busy Easter holiday period, which runs between Fishguard-Rosslare in Ireland.
Currently, companies are tendering for contracts for the work. According to Stena, the bids are being evaluated against criteria like "cost and time to install".