The Scottish Government is speaking to the RMT union this afternoon to urge them to call off the Cal Mac ferry strike and return to talks.
CalMac predicts the majority of services will run on Wednesday and Thursday.
Severe disruption on Friday will hit major vessel routes serving the Western Isles, Mull, Islay, Bute, Arran, Coll and Tiree.
If a service does run on any of these routes it is expected to be undertaken by a smaller vessel.
The government's resilience team has met to discuss the industrial action which will hit ferry services to the Western Isles and Inner Hebrides.
RMT urged to return to talks to avert ferry strike
23 June 2015
The RMT has announced its intention to undertake industrial action tomorrow, Thursday
and Friday -
With the strike set to go ahead, CalMac and Transport Scotland have made contact with bus, rail and aviation operators to see what additional services can be provided to help mitigate the impact.
CalMac have already started the process of contacting customers and updating their website to highlight the likely disruption on Friday.
Discussions with VisitScotland, the Scottish Tourism Alliance and Scottish Government officials are taking place to discuss what more can be done to bolster consumer confidence going forward, and also to raise awareness that the areas affected remain open for business during any action.
Speaking after updating cabinet colleagues and chairing a second resilience meeting in two days, Deputy First Minister John Swinney said: "Ministers are speaking to Calmac and the RMT this afternoon to urge them to call off the action and return to talks. I would urge both parties to continue discussions in an effort to reach an agreement that avoids damaging strike action.
"CalMac have issued more detailed information on their website and are speaking to their customers directly. We are all working together to try and minimise the impact of this industrial action at a crucial time for the islands’ economies that are served by these lifeline services.”
Transport Minister Derek Mackay said: "I have already provided assurances that a fair, affordable and sustainable pension scheme will be protected under the new Clyde & Hebrides Ferry Services contract.
"EU law requires the Scottish Government to tender ferry services. This was accepted by previous Governments when it initiated the first tendering exercise for CHFS, it is therefore regrettable that some are seeking to use the current situation to score political points.
"A record £1 billion has already been invested on port infrastructure, vessels and ferry services from 2007 to date, and we are determined to build on this track record. We have made clear our commitment to ensuring the continued delivery of safe and reliable services for ferry users.
"In the interim Cal Mac and my officials at Transport Scotland have made contact with bus, rail and aviation operators to see what additional services can be provided during this week's industrial action and we stand ready to support the islands during this testing time."