UPDATE 2.45pm: The RMT has followed the TSSA union in suspending strike action after an improved offer from Network Rail.
Talks between rail chiefs and union bosses are going to the wire over potential strike action taking place this bank holiday.
Representatives of Network Rail and TSSA returned to Acas today after two days of talks that have so far failed to yield a solution.
In fact, the tensions between the two have worsened after Network Rail issued a legal challenge, saying there were “serious defects” with TSSA's ballot.
But the group that manages the UK's entire train network said it was making its negotiating team available “all week and into the weekend if necessary”.
If the strike does go ahead, train services across the country will be severely affected.
Network Rail and the train operators are currently working together on contingency plans, and the full details of which services will be available is expected to be released on Thursday afternoon.
Network Rail chief executive Mark Carne said: “We believe there is a settlement to be had. I sincerely hope we can reach one...
“From the very start of negotiations we made clear that we want to reward our staff for the incredible job they do – but that any pay rise needs to be linked to smarter, more effective ways of working.
“We can't bank on the unions calling off the strike, so we are now concluding our contingency plans so passengers can make decisions about their journeys.”
He has written an open letter to passengers in which he urged them to plan for the worst.
He said: “I know how much you rely on the railway to take you to and from work and to meet friends and family and I know how businesses rely on the railway to move their goods around the country. For these reasons we are working closely with Acas and the trade unions to try to find the earliest possible resolution.
“If this strike goes ahead, many parts of the railway may be closed on Monday and Tuesday causing disruption to train services. I encourage you to plan ahead and check before you travel.”