A bus strike in West Vancouver could cut public transit service to BC Ferries' Horseshoe Bay Terminal by Friday, officials are warning.

Already this week an overtime ban has led to the cancellation of dozens of trips on the West Vancouver service since Monday.

Now, the union representing drivers and maintenance workers is warning there could be a full strike later this week that would shut down the entire service.

"That will mean that the buses will be off the road for some period of time by the end of the week," said Amalgamated Transit Union spokesman Bill Tieleman on Wednesday.

"That would remove the option of taking Blue Buses to the ferries," he said.

24 hours notice promised

It remains unclear when and if a strike will take place, but a statement on the District of West Vancouver website said a full strike could start as early as Friday morning.

"The District of West Vancouver understands the transit union is planning a full strike on Friday morning (October 21). We encourage Blue Bus users to make alternate travel arrangements for that day."

Along with about a dozen suburban routes, West Vancouver operates the main express bus service, the 257 route, which connects Metro Vancouver's public transit system to the BC Ferries terminal at Horseshoe Bay.

Greyhound and Tofino Bus also run buses about four times a day from the Vancouver bus station that connect with the ferries.

Tieleman said the union is still hopeful a full strike can be averted, but it is preparing to escalate job action shortly if there is no progress towards a deal.

"We'll give 24 hours notice to our riders to make sure they have alternatives for getting around, but we'll have more about it by the end of the day," he said.

The union's contract with the District of West Vancouver expired on March 31, 2016 and negotiations began in May.

Talks between the district and the Amalgamated Transit Union broke down Friday and the union was in a legal strike position Sunday.