Metro Vancouver mayors are urging parties on both sides of a regional transit dispute to resume negotiations after days of stalemate, saying some of the union's demands are impractical and escalated job action would hurt the region's most vulnerable people.

The Mayors' Council on Regional Transportation issued a statement Monday asking Coast Mountain Bus Company (CMBC) and Unifor, the union representing thousands of transit workers, to get back to the bargaining table and avoid an all-out strike.

"[The action] is impacting commuters and some of the most vulnerable residents in our region who rely on public transit," wrote mayors' council chair Jonathan Cote.

The first four days of the job action, which includes transit workers not wearing uniforms and refusing overtime, have seen more than 30 SeaBus trips cancelled. Unifor has said the action will escalate and begin affecting bus service by week's end if an agreement is not reached.

More than 30 SeaBus sailings were cancelled over the weekend as a result of job action by transit workers. (Maggie MacPherson/CBC)

The union wants an extra $608 million in wages, benefits and improvements to working conditions over 10 years.

The mayors' council statement said Unifor has suggested scaling back planned bus expansions for the next decade in order to cover the cost of the wage demands.

Cote said that option is "completely off the table."

"With North America-leading ridership growth, a climate emergency and growing road congestion, now is not the time to slow down transit improvements. Cutting the funding used to buy additional buses and hire more bus drivers will also do nothing to improve the working conditions for our valuable transit operators," the chair wrote.

Unifor western regional director Gavin McGarrigle speaks at a news conference in New Westminster, B.C., on Nov. 4. (Maggie MacPherson/CBC)

CMBC said in a statement Friday union demands would cost more than $608 million over 10 years. The company operates bus and SeaBus service on behalf of TransLink, the region's transit authority.

Speaking to reporters Monday, union representatives chided the mayors' council for its "one-sided" statement.

"[Coté] has taken the position of TransLink, where they're saying you cannot have an expanded system and take care of the workers. We are asking for people to have both," said Unifor western regional director Gavin McGarrigle.

People wait for a SeaBus at Waterfront Station in Vancouver on Friday amid job action by transit workers. (Maggie MacPherson/CBC)

A number of SeaBus sailings have been cancelled since Friday due to workers' refusal to work overtime, which has become normalized as part of sustaining regular service levels. Three more round-trip sailings have been cancelled for Monday afternoon between 4:10 p.m. and 7:45 p.m. PT.

Bus services haven't been disturbed by the job action thus far, but the union warned commuters can expect bus cancellations by the end of the week if the overtime strike continues.

"We've been very clear: unless these issues are addressed, this will escalate and it will end in a complete work stoppage," McGarrigle said Monday.

Watch how residents in North Vancouver and UBC reacted to the potential for no bus service:

Residents in North Vancouver and at UBC talk about how they would handle a full bus strike. 1:15

SkyTrain and HandyDart services have not been affected.

Metro Vancouver has not seen a full-scale transit strike in nearly two decades. A four-month walkout in 2001 crippled commutes for hundreds of thousands of people.