The Rail, Maritime and Transport union have joined the Transport Salaried Staffs Association (TSSA) rail union in suspending their planned Bank Holiday strike after receiving a new pay offer from Network Rail.
Members of the unions were due to walk out for 24 hours from 5pm on Monday.
TSSA leaders, and officials from the Rail, Maritime and Transport union have spent the last four days in talks with NR at the conciliation service Acas.
Manuel Cortes, general secretary of the TSSA, said: "Our negotiating team at Acas has received a revised offer from Network Rail.
"As a result of this, they have suspended the planned industrial action, pending the outcome of a meeting of our workplace representatives next week."
NR had been due to mount a legal challenge in the High Court later today against the TSSA's strike ballot.
The RMT, which represents most NR employees, announced it was also suspending its industrial action early this afternoon - Thursday.
RMT general secretary Mick Cash said: "Following the Acas talks, RMT has received a revised offer that enables us to suspend the planned industrial action while we consult in full with our Network Rail representatives."
The breakthrough came as workers, businesses and rail passengers were urged to prepare for the expected travel chaos if the strike by thousands goes ahead.
It's not yet clear whether the withdrawal comes too late to allow all cancelled services to be restored.
Before the latest announcement, East Coast services were expected to operate as normal until early on Monday afternoon (except in Scotland), but on Tuesday only a limited number of trains were expected to run between London and Leeds and London and York.
Other rail firms have already cancelled services on Monday and Tuesday and advised passengers not to travel unless the industrial action was called off.
