There are hopes that a deal may be struck soon to avoid more chaos on Scotland's railways.
The Aslef union said yesterday that train drivers are close to reaching an agreement with ScotRail despite rejecting its latest 4.2% pay offer.
Scottish organiser Kevin Lindsay told the BBC that more talks with the rail operator would take place on Monday.
He said the aim was to avoid industrial action by negotiating a deal acceptable to his members.
ScotRail has meanwhile introduced a temporary scaled-back timetable for Sunday services.
Mr Lindsay warned that the railways could be hit by a series of 24-hour strikes if the issue is not resolved.
ScotRail, which was nationalised by the Scottish government in April, is currently running a greatly-reduced timetable after many drivers refused to work overtime or on their rest days over the dispute.
Last week, the operator added extra services to its emergency timetable on Friday and Saturday.
But it did not put a Sunday timetable in place, resulting in services being delayed and cancelled at the last minute.
On Thursday, ScotRail announced to customers: "We're introducing a temporary timetable for Sundays too, so we can provide greater certainty and reliability for our customers.
"It will be available to view on our website and app from Saturday morning."
Aslef has previously rejected a 2.2% pay deal, before later being offered 4.2% and improved conditions - which Transport Minister Jenny Gilruth said she was "hopeful" would be accepted.
But the union announced on Wednesday that its national executive had rejected the offer and would ballot for industrial action unless further talks were held.
ScotRail said it was frustrated by the decision, and "astonished" that the union had decided not to put the improved pay offer to its members.