The Fraternal Order of Transit Police Lodge 109 is calling for SEPTA to enter binding arbitration to end the impasse.
The union said in a statement that it is "willing to make substantial concessions and even surrender its right to strike if SEPTA would agree to accept neutral arbitration."
Union leaders said the arbitration process is standard with police forces across Pennsylvania.
SEPTA said it received a formal proposal from the union on Thursday and wants to continue negotiations at the bargaining table.
"SEPTA is committed to working with the FOTP on a contract that is both fair to Transit Police officers and responsible to the fare-paying riders and taxpayers who fund the Authority," a SEPTA spokesperson said in a statement.
That update comes just weeks away from the start of the World Cup games in the city, America's 250th anniversary and the MLB All-Star Game.
The current contract ended in March.