WASHINGTON (AP) — Two years ago, the Federal Communications Commission stumbled as it tried to create a nationwide wireless broadband network for police officers, firefighters and emergency medical workers, delaying the construction of what everyone agrees is an urgently needed system.

Now the agency is hoping to rework the plan, which relies on a prime slice of airwaves called the D Block. But many public safety officials say the commission is, once again, going about it the wrong way.

In 2008, the FCC attempted to auction off the block to the wireless industry, with a requirement that the winning bidder help build out a sturdy communications network that would be shared with first responders and give them priority in an emergency. But those conditions proved too onerous, and the auction failed to attract any serious bidders.

So this time around, the agency hopes to auction off the D Block to wireless carriers and use the proceeds — projected to be as much as $4 billion — to help pay for a public safety network on a separate slice of spectrum already set aside for first responder broadband use. In frequency terms, the existing public safety airwaves are right next door to the D Block and just as big. Both pieces of spectrum were freed up in last year’s transition from analog to digital TV signals.

The existing public safety block, the FCC says, provides plenty of capacity for day-to-day operations — letting first responders access everything from surveillance video to fingerprint databases using laptops and handheld devices in the field. And in an emergency, the FCC proposal would give public safety users priority access to the D Block and other airwaves from the digital transition.

The FCC says its proposal would fulfill a Congressional requirement to auction off the D Block and ensure public safety benefits from the latest wireless technology.

“We have a brief technological window to get everybody on the same page from the beginning and build a 21st Century … broadband system,” says Rear Admiral James Barnett, head of the FCC’s Public Safety and Homeland Security Bureau.

But the FCC proposal has run into fierce resistance from public safety leaders who warn that their current spectrum holdings are not big enough to meet their needs. They are wary of relying on commercial networks to fill the gap, particularly in emergencies, and are calling on the government to give the D Block to them so they can combine it with the adjacent airwaves and double the amount of spectrum dedicated to public safety broadband.

“If they auction this spectrum, we’ve lost it forever,” says Rob Davis, head of the San Jose Police Department and president of the Major Cities Chiefs of Police Association. “We need to control this network ourselves.”

Public safety officials have powerful allies in Congress, including Senate Commerce Committee Chairman Jay Rockefeller, D-W.Va., and Sen. John McCain, R-Ariz. But House Commerce Committee leaders are drafting legislation based on the FCC plan.

The big wireless carriers have also joined the fray. T-Mobile USA and Sprint Nextel Corp., eager for more spectrum, support the FCC proposal. Verizon Wireless and AT&T Inc., both flush with spectrum from 2008 auctions of other airwaves from the digital transition, want to see the D Block go to public safety. So does Motorola Inc., which dominates the market for first responder communications equipment and handsets.

The one thing everyone agrees on is the need to bring nation’s public safety communications networks into the digital age.

The shortcomings of the existing networks became apparent after the 9/11 attacks and Hurricane Katrina, when police officers, fire fighters and other first responders could not talk to one another because they were using incompatible — and sometimes antiquated — systems. One recommendation of the 9/11 Commission was the construction of a nationwide “interoperable” wireless network that would let public safety workers across agencies and jurisdictions communicate with each other.

The FCC insists its proposal, part of its national broadband plan, would meet the needs of first responders. The spectrum already dedicated to public safety, Barnett says, can handle day-to-day operations since advanced 4G wireless technology can make far more efficient use of airwaves than public safety networks do today.

And in a big emergency, he warns, even the bigger block of spectrum envisioned by the public safety plan might not be enough. The FCC’s proposal would give public safety first dibs on at least three times more spectrum in a crisis.

But Chuck Dowd, deputy chief in the communications division of the New York City Police Department, says commercial networks are just not reliable enough for first responders who deal with life-and-death matters. Richard Mirgon, president of the Association of Public-Safety Communications Officials International, adds that in a mass emergency, commercial networks are often already overwhelmed — making it impossible for first responders to even connect to them.

With the dispute now heading to Congress, the focus is on funding.

Bruce Gottlieb, chief counsel to FCC Chairman Julius Genachowski, says the FCC plan would drive down the cost of a first responder network by allowing public safety to piggyback on the massive investments being made by commercial wireless carriers as they upgrade their technology.

The agency’s plan puts the cost of building the public safety network at roughly $6.5 billion and the cost of operating and maintaining it at between $6 billion and $10 billion over 10 years — less than half the cost of a stand-alone network, the FCC says.

In the face of a ballooning federal deficit and state and local budget cuts, Barnett insists, the FCC plan offers the best way to come up with this funding.

But public safety officials are confident they can find the resources to pay for a broadband network even without D Block auction proceeds. If they get the D Block, they say, they would be able to lease excess airwaves to commercial carriers since they would not always need all of it.

What’s more, another key recommendation in the FCC’s national broadband plan is a proposal to free up a lot more spectrum for wireless broadband over the next 10 years. That, public safety officials say, will produce plenty of revenue to pay for a first responder network.