Arriva Trains Wales has confirmed the 24-hour strike by driver unions Aslef and RMT is expected to go ahead on Monday following a failure to resolve a row over pay and conditions.
The strike action will result in the cancellation of all Arriva Trains Wales services on Monday and may also cause some early-morning disruption on Tuesday.
Arriva runs services throughout the county, including the Cardiff to Manchester service that travels through Ludlow, Shrewsbury and Whitchurch, and trains from Birmingham to Aberystwyth that include stops at Telford, Wellington and Newtown.
Aslef also confirmed its members will walk out on Monday.
The union said an overtime ban which started earlier this week was already having an impact, claiming that like many train operators, Arriva Trains Wales relies on drivers working overtime. The union dismissed company claims that a new offer had been made.
Simon Weller, Aslef's national organiser, who is leading negotiations for the drivers, said: "The company has not made a new offer.
"It has sent us a form of words. But it is not new and it is not an offer."
Aslef said it was available for talks to resolve the dispute, but added there was nothing at the moment to discuss.
The pay side of the dispute has been accepted, but Aslef claims the company is trying to "railroad through" changes to terms and conditions.
Arriva Trains Wales officials say they are "disappointed" that Aslef hasn't accepted their latest offer over pay and conditions.
The transport operator says it "deeply regrets" the disruption and is continuing to do all it can to avert strike action by Aslef.
However, it is advising people to make alternative travel arrangements for Monday, and also to check their travel plans for Tuesday morning.
As the action will impact the entire Arriva Trains Wales network, which includes Shropshire, it will not be possible for replacement bus services to be provided as the firm said there are insufficient numbers of buses available to use to cover the 1,000-plus services operated each day.
Gareth Thomas, human resources director for Arriva Trains Wales, said: "We are extremely disappointed that the train drivers union's national executive have not accepted our latest offer of improvements to terms, conditions and pay for their members, and that they have opted to take industrial action, even though we submitted a revised proposal to them on December 23 following productive pre-Christmas talks.
"Directors at Arriva Trains Wales have been in contact almost every day with union officials in a bid to resolve this issue and stress the urgency of the situation if disruption to customers was to be avoided."
Arriva Trains Wales also said an indefinite train driver overtime ban is also currently in force which may impact some timetabled services until the dispute is resolved.
An Aslef spokesman said that while a deal on pay had been agreed, there was still a dispute over terms and conditions.
Further information, including special ticket arrangements for customers to complete journeys at other times, ticket acceptances with other rail operators and ticket refunds, can be found at www.arrivatrainswales.co.uk/ia2016 and from railway station ticket office staff.