Under a law which dictates seven days' notice of disruption, the executive of the RMT transport union is expected to call at least one more 24-hour stoppage next week to follow this Wednesday's strike.
While there was no persistent demand at last week's RMT conference for tougher action, some executive members have been angered by management's decision to bypass the union and send letters directly to the 4,000 signal workers.
If the 21-man executive decides to intensify the battle, some officials have canvassed the idea of strikes on Mondays and Fridays.
The leadership will hear an account of the abortive talks with management last week from Vernon Hince, the chief negotiator, and reports on morale among members. A national official said last night that there was no sign of a weakening of resolve, although there is no clamour among members for an intensification of disruption.
Railtrack, the state-owned company which runs the industry's infrastructure, believes there could be a greater chance of a settlement now that the RMT's activist-dominated conference is over.
The conciliation service, Acas, is today expected to extend an informal invitation to both sides to renew negotiations, possibly tomorrow, so that management can 'clarify' its offer. But RMT said last night it would not agree to more talks simply to 'go through the motions'.
The time available for negotiations means the chances of averting the stoppage on Wednesday are limited.