Scotrail has warned trains will be cut due to an ongoing shortage of drivers.
In a statement, Scotrail said was looking at how it can deliver greater timetable certainty and reliability for customers.
A spokesman said there would be more to say in the “coming days”.
Aslef, who represent the majority of train drivers in Scotland, said it expected the news from Scotrail would be that a third of trains would be dropped from the timetable.
Kevin Lindsay, Aslef’s Scottish organiser said: “These cuts are the biggest cuts to services since the dark days of Beeching.
Railways are being dismantled
“We will not stand aside and watch our railway being dismantled as a consequence of appalling mismanagement and a failure to recruit enough drivers.”
He said any plans to cut trains would fatally undermine the Scottish Government’s own climate targets, and commitments they gave in relation to the future and importance of rail at Cop26.
“Aslef has repeatedly called for the resumption of talks over pay and other outstanding issues but the Scottish Government has refused to allow Scotrail to get back round the table,” he continued.
“Today we are calling for the immediate withdrawal of these proposed service cuts, and the urgent resumption of negotiations to discuss pay, conditions and how we can work together to end the driver shortage.
“We recently produced ‘A Vision for Scotland’s Railways’ which would deliver a clean, green, reliable and affordable railway that all of Scotland can be proud of.
“Scotrail and the Scottish Government should work with us to help implement this visionary plan for our rail services.”
People travelling at weekends have already experienced difficulties with last minute cancellations to West Highland Line services.
David Simpson, ScotRail service delivery director, said: “We are experiencing a driver shortage, which means some services will be cancelled.
“We are very sorry for the disruption and inconvenience this will cause and understand customer frustration when this happens.
Ballot for strike action
“If you’re travelling on the ScotRail network, please check your journey before travel by downloading the ScotRail app or visiting scotrail.co.uk.
“Unfortunately, since the drivers’ union Aslef announced it would ballot for strike action, a significant number of drivers, but not all, have declined to make themselves available for overtime or rest day working.
“While rest day working is entirely voluntary this does mean we do not have the number of drivers available to operate the full timetable.
Mr Simpson continued: “We are currently reliant on drivers working overtime or on their rest days because of delays to training new drivers caused by the pandemic. This is something experienced by all operators across Britain.
“ScotRail has made a good offer that could potentially deliver an overall pay package worth a 7% increase for staff.
“This gives hard-working staff a well-deserved pay rise, recognises the cost-of-living challenges faced by families across the country, and delivers value for the taxpayer.”
