Leaders from five cities along Highway 78 agreed Monday to explore ways they could cooperate financially to help Escondido build a large stadium that would keep the San Diego Chargers in the region.

During a special meeting Monday that was closed to the media, officials from Escondido, Oceanside, Carlsbad, Vista and San Marcos discussed how a stadium would benefit North County as a whole and what the hurdles are to such an ambitious project, Escondido Mayor Lori Holt Pfeiler said.

One key topic was whether other cities have land along the Sprinter rail line for one or more private developments that would be connected financially to the stadium, Pfeiler said.

Chargers officials say they need as much as $400 million in revenue from such an ancillary private development to help pay for the $900 million stadium. A partner city is necessary because Escondido's economy is not perceived to be large enough to absorb so much new development, whether it be offices, housing, retail or a combination of those.

Team officials recently added Escondido to the short list of cities under consideration for a new stadium, and an aging industrial sector near Highway 78 and Interstate 15 has been identified as a prime potential location.

But new momentum behind a stadium project in the City of Industry this fall has cast doubt on whether the Chargers will stay in San Diego.

At Monday's meeting, potential sites for an ancillary development in North County were discussed, Pfeiler said. But she stressed that the goal of the conference was not to delve into specifics.

Instead, the city leaders agreed to begin a long and complicated dialogue about finding a regional solution to the Chargers' need for a new stadium to replace outdated Qualcomm Stadium in Mission Valley, she said.

The meeting, which was held at the McMahan House on the campus of Cal State San Marcos, was organized by the San Diego North Economic Development Council.

During the meeting, the council agreed to revive a Chargers task force created in 2007 when Oceanside was a prime candidate for a new stadium. Gary Knight, chief executive of the council, said the revived task force would probably have different members than before.

Pfeiler said she was pleased by the sense of cooperation at the meeting.

"I feel very optimistic that we as a region understand that it's going to take a some heavy lifting," Pfeiler said.

Oceanside City Councilman Rocky Chavez agreed.

"It was refreshing to have five cities coming together to solve a problem," said Chavez, explaining that another recent example of such cooperation was a regional network of North County homeless shelters established in 2007. "We're more connected than ever since the Sprinter began running (in March 2008)."

But despite the optimism, Vista Councilman Bob Campbell said the hurdles are formidable.

"It was a good first step," Campbell said. "But the biggest elephant in the room was the economics."

Knight has agreed to research the economic benefits enjoyed by other cities located near new stadiums and to gather data from other cities that have wooed the Chargers, including Oceanside, Chula Vista and National City. He said such analysis would be reported back to the city leaders at a subsequent meeting.

In addition, the North County Transit District has agreed to study the capacity of the Sprinter, the Coaster and a rapid bus system planned along Interstate 15 to help determine the feasibility of a North County stadium, Campbell said.

Meanwhile, Pfeiler said that Escondido and San Diego officials have agreed to jointly study the leading Escondido site and two potential stadium sites in downtown San Diego to determine the advantages and disadvantages of all three sites.

Mark Fabiani, general counsel for the Chargers, said Monday that he was pleased that North County officials had started working together.

"This signals that this is a regional issue and that there may be a regional solution," Fabiani said.

Call staff writer David Garrick at 760-740-5468.