OAKLAND — Painting a grim picture of the city’s chances of keeping the Raiders from moving to Las Vegas, NFL Commissioner Roger Goodell told Mayor Libby Schaaf in a letter Friday that the Ronnie Lott-led Oakland stadium proposal is filled with uncertainty.

In the letter obtained by this news organization Saturday, Goodell wrote that the city’s proposal is not “clear and specific, actionable in a reasonable time frame, and free of major contingencies.”

The criticism from the NFL’s top executive came days before NFL owners are expected to vote on the team’s relocation to Nevada and in response to an earlier letter from Schaaf outlining the $1.3 billion development at the Coliseum complex.

Hall of Famer Lott and his investors have proposed building a 55,000-seat football stadium, along with hotels, restaurants and space for a new ballpark for the A’s.

Meanwhile, in Nevada, the Raiders have proposed building a $1.9 billion, 65,000-seat domed stadium near the Las Vegas Strip, relying heavily on $750 million in taxpayer money and a $650 million loan from Bank of America.

“Key issues that we have identified as threshold considerations are simply not resolvable in a reasonable time,” Goodell wrote of the Oakland proposal.

Part of the commissioner’s concerns center on the A’s long-term lease at the Coliseum, a facility they have shared with the Raiders for decades.

Schaaf has previously said the NFL requested that the city “truncate” the lease, and she hoped the request was not a “take-it-or-leave-it condition.” Goodell, in his letter, said, “the long-term nature of the commitment to the A’s remains a significant complication and the resolution of that issue remains unknown.”

“We also accept that you do not wish to exercise (and may not be able to exercise) the contractual termination rights related to the A’s,” the commissioner noted.

Lott’s proposal, which includes a $600 million commitment from money-management firm Fortress Investment, sets aside 15 acres for the A’s, if they choose to stay at the Coliseum.

At a rally with fans on Saturday, Schaaf said there is no conflict with the A’s, and the city has given the NFL as much detail as it can.

“We have gotten as clear as we can get without the Raiders at the table,” Schaaf told the crowd inside the Coliseum. “We need the Raiders at the table.”

City officials have said that it has been more than a year since they have met directly with the team’s owner, Mark Davis, who has committed to the Las Vegas deal.

Goodell acknowledged and thanked Oakland city officials, specifically Schaaf, for being “accessible, creative and diligent in exploring alternatives.”

“Despite all of these efforts, ours and yours, we have not yet identified a viable solution,” Goodell said. “It is disappointing to me and our clubs to have come to that conclusion.”

NFL owners are expected to vote on the relocation to Las Vegas on Monday in Phoenix. Davis needs 24 of the 32 owners to approve the team’s third move in 35 years. According to Goodell, the owners will also review the efforts to keep the team in Oakland.

Earlier this month, Schaaf was among a group that presented Oakland’s plan before the NFL’s Finance and Stadium committees, which consist of 18 owners. The committees “will be presenting their analysis and recommendations to the full membership next week,” according to Goodell.

Raiders fan Rob Rivera, one of the creators of the “Black Hole” contingent at Raiders games, pointed to a sign that said “if you build it, we won’t come” as he addressed the rally attendees.

“This here that we won’t come, is true,” Rivera said.