SEPTA's Regional Rail engineers moved a step closer to being able to strike early next year, after the National Mediation Board on Thursday ended its efforts to broker an agreement.

The board on Thursday declared an impasse in negotiations and suggested the two sides submit their long-running dispute to binding arbitration.

The 220 engineers, represented by the Brotherhood of Locomotive Engineers and Trainmen, said they would accept arbitration, but SEPTA will not, spokeswoman Jerri Williams said.

The next step, under federal railroad labor laws, will be for the mediation board to release the parties from mediation.

That would start a 30-day "cooling off" period and a 240-day dispute-resolution period required before a strike or lockout would be permitted.

That period would expire in January, assuming that a presidential board is created promptly to investigate the long-running contract dispute.

Engineers have been without a new contract since 2010.

The engineers last went on strike against SEPTA for 108 days in 1983, after the transit agency took over operation of the Regional Rail system from Conrail.

If they were to strike in concert with bus drivers and subway operators, it could create the first-ever shutdown of SEPTA's entire transit system: buses, subways, trolleys, and trains.

Contracts with transit workers expired in March and April, and no talks have been held recently between SEPTA and the Transport Workers Union Local 234, which represents about 5,500 bus drivers, subway and trolley operators, and mechanics.

TWU local president Willie Brown said the breakdown of SEPTA's negotiations with the engineers "doesn't affect us one way or the other . . . except to show that we're both dealing with the same monster."

He noted that SEPTA also declined binding arbitration in its negotiations with the TWU.