PATCO riders will soon be able to use their Freedom cards to pay fares on SEPTA subways and buses, PATCO and SEPTA officials said Wednesday.

However, SEPTA-issued smart cards won't work on PATCO.

After SEPTA switches to its long-awaited electronic "smart card" fare-payment system this year, PATCO cards will be compatible with the SEPTA Key system, PATCO general manager John Rink said.

One caveat: A PATCO card must be registered with PATCO. That registration will permit SEPTA to identify the user and bill PATCO for the trip, Rink said.

SEPTA's new "open payment" system will allow riders to use any contactless credit card or a SEPTA-issued Key card, or even a smartphone app, to pay fares at card-reading turnstiles or bus-fare boxes. Contactless cards are embedded with a computer chip that communicates with a chip-reader at a turnstile or cash register.

But PATCO's system is a proprietary, "closed" system that currently accepts only the PATCO-issued Freedom card.

PATCO's fare system, built by Cubic Transportation Systems Inc. of San Diego, could be modified to accept any contactless credit card, just like SEPTA's. In fact, it once was.

In 2011 and 2012, Cubic reengineered the PATCO system to allow the use of contactless cards during a yearlong experiment.

But PATCO officials decided the cost for processing the transactions was too high, and the contactless-reading capability was removed from PATCO's turnstiles in 2012.

Kevin O'Brien, senior program manager for SEPTA's smart-card system, said SEPTA's Key cards might eventually be accepted by PATCO, as officials of the transit agencies continue to negotiate contracts and compatibility agreements.

SEPTA's $130 million smart-card system will be rolled out this year for buses, subways, and trolleys, but not until at least next year for Regional Rail trains. O'Brien said Wednesday that no specific date had been determined for the launch of the system, which has been in the works since 2007.