OAKLAND — Local leaders aren’t cutting the cord on the Coliseum City megadevelopment, but the initial plan submitted last month has gotten a chilly reception, especially from Alameda County officials, sources said.

Oakland and Alameda County have until Monday to respond in writing to Floyd Kephart’s $4.2 billion plan for transforming the sprawling coliseum complex in East Oakland into a minidowntown and helping the Raiders build a new football stadium there.

Kephart, a San Diego-based finance professional, will get 15 days to respond to the confidential joint city-county letter. He’ll have until Aug. 21 to produce a final development plan for Coliseum City, which envisions building 4,000 homes, a shopping center, hotel and enough office space to fill three Transamerica Pyramid buildings between the Coliseum BART station and Interstate-880.

“At this point, the process is going to continue,” assistant city administrator Claudia Cappio said. “The ball gets popped back into his court.”

With the NFL threatening to let the Raiders return to Southern California if no stadium deal is reached this year, Oakland officials are also open to negotiating directly with the team, but there hasn’t been any recent activity on that front. The two parties last spoke in mid-June, Cappio said, which is before Kephart submitted his plan.

The city most recently discussed stadium opportunities for the Oakland A’s about two weeks ago, she added.

Kephart faces a tall order in getting the city, county and Raiders to sign onto the proposed development project.

While the Raiders have refused to comment on his initial stadium financing plan, it was quickly panned in NFL circles for making the team responsible for building a 55,000-seat, $900 million stadium that would be smaller and have less revenue potential than a proposed stadium in Carson.

Raiders ownership also would have to sell off 20 percent of the club to a company led by Kephart for $200 million and pump half of that into stadium construction.

For local officials who have been opposed to any public stadium subsidy, Cappio said that key issues include how Kephart would finance the project, including hundreds of millions of dollars for roads, sewers, utilities and parking garages needed to transform the site into an urban center.

Council members met in private Thursday to discuss the proposal, Cappio said. Kephart did not attend the meeting.

The city and county’s written response to Kephart will provide feedback on all of the reports he produced in June, including the financing plan, feasibility study and community benefits analysis. Kephart’s suggestion that the city and county be responsible for benefits such as affordable housing spurred quick opposition from community groups.

“I’m sort of looking and searching for the community benefit side of it,” Alameda County Supervisor Richard Valle said when asked about Kephart’s proposal last week. “I haven’t seen it.”

Kephart is continuing to work on the project and is awaiting the written response, his attorney Zach Wasserman said. Acknowledging that Alameda County supervisors have never been as bullish on Coliseum City as their counterparts in the city, Wasserman wouldn’t rule out a final deal that bought out the county’s stake in the site and took it out of the already complicated equation.

“That’s certainly still on the table,” he said. “How that would work, we don’t really know … but it would simplify things. No question about that.”

Contact Matthew Artz at 510-208-6435.