The rail strike scheduled for this weekend could be called off if train operator Northern meets the union's guarantees on having a second member of staff on board services.
The RMT says it will suspend what would be its 38th day of industrial action on Saturday if a number of crucial conditions are met.
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The move raises the possibility of further talks with arbitration service Acas and a possible end to the safety row which has involved months of weekend strikes.
This week the authorities have been keen to distance themselves from driver-only operations fearing industrial action will cause transport chaos during the festive season.
A statement from the RMT's executive said: "This union is and always has been available for talks and we are prepared to engage in talks immediately via Acas.
"We welcome the correspondence from Transport for North, the Department for Transport and the company. We note however that Arriva Rail North have not made any clear proposals to this union to resolve this dispute.
“We are available across the weekend and would welcome talks commencing as soon as possible and further reiterate our numerous previous requests for tripartite talks with both the company and DFT.
“In addition, we will be prepared to suspend the industrial action planned for Saturday December 1 providing that clarity is received from the company regarding ‘a new proposal that will see the retention of a second person on-board trains’ and specifically around the following three points.
"One, there is an absolute 100 per cent guarantee that no trains will run without the second member of staff on board.
"Two, that the second member of staff will be clearly designated as safety-critical to the running of all services.
"Three, that the second member of staff will retain the full suite of safety and operational competencies of the guard, including a direct role at the platform/train interface and train despatch."
The RMT says its members will not down tools if its conditions are met by noon on Friday.
RMT general secretary Mick Cash said: "Firstly I want to pay tribute to the RMT members and our supporters from the travelling public whose solidarity and determination have been instrumental in getting the focus of the dispute back on to the guarantee of a second person on the train.
“It is now imperative that the company clarify the role and safety critical status of that second person as set out by our executive to allow for a suspension of this weekend’s action and for talks to take place."