Red Funnel has said it intends to keep sailing, albeit to a reduced timetable, on dates of proposed strike action.
Around 120 Unite members, employed by the firm, will walk out in a dispute over pay.
Unite said Red Funnel’s treatment of workers has been "disgusting" as it vowed to plough ahead with industrial action.
In response to the confirmed strike dates, Red Funnel said it will share a revised timetable in due course.
A spokesperson said:
"We expect to keep sailing on these dates, albeit to a revised vehicle ferry timetable. Our Hi-Speed Red Jet service is expected to operate as scheduled.
"Now that we have dates in hand, we can proceed to finalising an updated timetable, which we intend to share by Wednesday, 13 July. In the meantime, we ask that customers bear with us and please refrain from calling our contact centre team with related queries at this time.
"As ever, our priority is to ensure the Island community remains connected and that we continue to provide our lifeline service.”
Dates of strike action can be found here.