Last-ditch talks have been held in a bid to avert the first national rail strike since 1994, which could cause travel disruption over Easter.
Rail workers will take strike action on the four days after Easter in a dispute over jobs and working practices.
The RMT union and Network Rail met at conciliation service Acas, although the outcome is not yet known.
Talks between Network Rail and the RMT and TSSA unions at conciliation service Acas failed to reach agreement.
Signal workers and maintenance staff belonging to the RMT voted for walkouts in a row over job cuts and conditions.
TSSA supervisors and RMT maintenance workers will walk out from 6-9 April, while RMT signal staff will strike from 0600-1000 and 1800-2200 the same dates.
Infrastructure operator Network Rail says most services would be cancelled if a strike was announced.
Infrastructure operator Network Rail has said most services would be cancelled if a strike was announced.
The RMT says options for action include a strike and an overtime ban.
'Public safety'
Network Rail said talks held on Wednesday had yielded "progress".
RMT general secretary Bob Crow said: "RMT negotiators have worked flat-out to try and reach an agreement that protects rail safety, job security and working agreements in the disputes involving signalling and maintenance staff on Britain's railways.
A spokesman said: "Network Rail is committed to pursuing a negotiated settlement - our door is always open to further discussions."
"Despite long hours of talks, we have received nothing concrete from Network Rail that addresses the key issues."
TSSA general secretary Gerry Doherty said the strike was all about "the safety of the travelling public and the safety and security of our members".
He added that the firm "will do everything it can to run trains to minimise disruption to passengers" in the event of a strike, adding that its contingency plans were at an "advanced stage".
Transport Secretary Lord Adonis said: "A strike is in no one's interests and could cause serious disruption to passengers.
Negotiations over its plans to cut 1,500 maintenance jobs started this week and also involve the Transport Salaried Staffs Association, which also represents maintenance workers.
"Both sides should seek to resolve this dispute by negotiation and not confrontation and I am urging them to do so."
An RMT spokesman said that a warning of action was premature when talks were adjourned on Wednesday.
However, BBC transport correspondent Richard Scott said that, if no last-minute deal was reached, strike dates were expected to be announced.
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It has said 1,100 workers have already volunteered for redundancy and the "vast majority" of the cuts will be achieved without resorting to compulsory lay-offs.
The RMT claims passenger safety is being put at risk, something which Network Rail denies.
RMT general secretary Bob Crow said the ballot in favour of strikes demonstrated members' opposition to cuts and to "the assault on jobs and working conditions".
The talks came as rail maintenance company Jarvis announced that it would go into administration after lenders refused to offer the company further credit.
Jarvis said: "Following negotiations with the company's secured lenders, it has today become clear that sufficient support will not be extended to the company to enable it to continue trading as a going concern."
The company has seen big reductions in its business since the beginning of the recession in 2008.
