The week-old strike by SEPTA's police force is costing both sides more money than they can expect to gain if they win at the negotiating table.

But the fight is not just about 35 cents an hour in pay. It is about future contracts, not only for the police but for 16 other SEPTA unions.

The 219 striking officers are losing, on average, $1,357 a week each. It would take an officer nearly two years to make that up if he or she received the additional 35 cents an hour the union is striking for.

Meanwhile, SEPTA is spending about $128,000 a week on temporary security guards and overtime pay for city police. But the agency will only save about $3,000 a week by not paying the 35 cents an hour to the police.

The Fraternal Order of Transit Police went on strike March 21. The police had been working without a contract since their last pact expired March 31, 2011.

The sticking point is the difference between the union's request for a 50-cent-an-hour "recertification" payment and SEPTA's offer of 15 cents an hour.

Officers must meet annual police certification requirements to keep their jobs. The union argues that the officers should be paid extra for meeting those requirements, as are SEPTA locomotive engineers, who get a 57-cents-an-hour certification payment.

The union and SEPTA had agreed before the strike on the broad parameters of a settlement, in line with the precedent-setting "pattern contract" signed in 2009 with SEPTA's largest union, Transport Workers Union Local 234, which represents bus drivers, subway and trolley operators, and mechanics.

That would give the police an 11.5 percent salary increase over the five years of the contract, and an immediate $1,250 "signing bonus" for each officer.

The current starting annual salary for officers is $34,612, topping out at $57,351. SEPTA says that, including overtime pay, the typical officer now collects $62,789 a year. An 11.5-percent increase would boost that to $70,600 after five years.

The transit police are seeking the recertification pay as a way of getting a small additional increase beyond the pattern set by the TWU contract.

They argue that a state fact-finder, brought in by the Pennsylvania Labor Relations Board last year, endorsed other increases, such as higher meal payments and uniform allowances, that would have cost SEPTA much more than the 50 cents an hour they are seeking.

And the police see the 50-cent-an-hour boost as a way to build a higher base on which to build future contracts.

Unlike city police and firefighters, transit police are not allowed to take their wage and benefit demands to binding arbitration, where a three-member panel determines the final outcome.

So they see a strike as their only leverage in the long-term negotiating process.

SEPTA, meanwhile, insists that any increases beyond the pattern set by the TWU contract will be demanded by the 16 other unions and would cost SEPTA millions of dollars a year.

In its annual operating budget of $1.28 billion, SEPTA assumes certain labor expenses for each union, based on the pattern contract.

"What the police are asking for exceeds that box," said SEPTA spokesman Richard Maloney. "If we were to break the precedent, the rest of the unions would naturally ask to be there, too. And that would cost millions and millions of dollars."

The sides are scheduled to return to the bargaining table Wednesday.

The union warned Tuesday that without transit police, passengers were risking their safety by venturing onto SEPTA buses and subways.

"People are scared, and eventually that will erode confidence in the system," said union spokesman Anthony Ingargiola, noting that thousands of visitors are likely to be headed to South Philadelphia for Bruce Springsteen concerts on Wednesday and Thursday and for exhibition Phillies games on Monday and Tuesday.

The union cited 28 thefts and robberies at SEPTA locations in the first five days of the strike, a rate of more than five per day, compared with the average of one per day in 2011 (a reported 415 thefts and robberies for the year).

Maloney, the SEPTA spokesman, said the subway and bus system remained well-protected with hired guards and city police. He said SEPTA officials are reviewing the recent incidents with police, "but we have not seen anything out of the ordinary."

Contact Paul Nussbaum at 215-854-4587 or pnussbaum@phillynews.com.