Developer Douglas Manchester has written to the National Football League, expressing interest in developing a privately financed stadium on the current Mission Valley site of Qualcomm Stadium.

“This is premature but I am doing everything in my power to keep an NFL team in San Diego and working to get cooperation of the City Council,” Manchester said in an emailed statement on Feb. 15. “We need a team here that wants to be here.”

A letter sent by Manchester to NFL Commissioner Roger Goodell on Feb. 8 – obtained by the San Diego Union-Tribune from an undisclosed source – said the developer has “assembled a powerful group of associates” ready to develop the 166-acre Mission Valley site with elements including a new 70,000-seat stadium, at no cost to taxpayers.

The developer said the project could provide “an immediate alternative” for the Oakland Raiders if that team’s current proposal to relocate to Las Vegas falls through. Under that scenario, the Raiders would replace the former San Diego Chargers, whose owner Dean Spanos recently moved the team to Los Angeles.

The NFL and Manchester have since declined to provide further details related to the correspondence. NFL owners are expected to vote on the Raiders’ Las Vegas relocation at a meeting in late March.

Manchester, who at the time owned the Union-Tribune, advocated in 2012 for a downtown waterfront stadium and entertainment complex on the current site of the Tenth Avenue Marine Terminal. That concept did not garner widespread civic support and was openly opposed by entities including the Unified Port of San Diego.

The developer’s latest proposal comes as another investment group, led by San Diego’s FS Investors, is gathering signatures for a plan to build a privately financed mixed-use development at the Mission Valley site that would include a stadium to house Major League Soccer and potentially San Diego State University football games.

The investment group is aiming to present approximately 72,000 voter signatures to San Diego City Council, which would have the option of approving the proposal or placing it on a future election ballot. That investment team has applied to bring a new MLS team to San Diego, but also plans to reserve about 15 acres for potential future development of another facility that could house pro football if the city is able to bring in another NFL team.

The investors are seeking to purchase the Mission Valley site from the city at market rate, then privately develop more than $1 billion in amenities including offices, stores, restaurants, apartments and civic spaces. The group’s soccer-oriented stadium, with about 30,000 seats, is expected to cost around $200 million, with costs potentially to be shared with SDSU.