The union representing SkyTrain workers says it has issued 72 hours strike notice after four days of mediation failed to produce any significant progress.

The notice means the union will be in a legal position to strike as early as 11 a.m Monday.

"We are still committed to reaching an agreement at the table, and our committee will make itself available day and night, over the weekend, to reach a fair deal without any interruption of service," said CUPE 7000 president Tony Rebelo in a news release.

Both parties are still in bargaining. The union says it will provide an update on its planned job action Saturday at 11 a.m.

CUPE 7000 represents approximately 900 SkyTrain workers who provide service as attendants and control operators, as well as administration, maintenance, and technical staff. Their employer, the BC Rapid Transit Company, operates and maintains the Expo Line and the Millenium Line on behalf of TransLink.

The Canada Line and the West Coast Express are not affected.

Two weeks ago, CUPE 7000 members voted 96.8 per cent in favour of job action after months-long talks broke down.

The vote gives the union the option of taking measures such as refusing overtime or going on strike.

The BC Rapid Transit Company says in a statement that is doesn't know what form the job action will take or when it might start.

"We are hopeful and committed to reaching a fair deal without disrupting the valuable service we provide to the residents of this region," company president Michel Ladrak said in a statement.

Rebelo says bargaining is focusing on key issues around wages, forced overtime, staffing levels and language around trades.