OAKLAND — Oakland is preparing to sue the NFL and the Las Vegas-bound Raiders, and it could mean the Raiders will leave Oakland earlier than expected.

Multiple City Hall sources familiar with the matter have confirmed to this news organization that a lawsuit against the league and the Raiders is expected to be filed and announced soon by City Attorney Barbara Parker.

Parker’s office is preparing to file an antitrust suit that could seek millions of dollars in damages, according to the sources who were not authorized to discuss the lawsuit. Three outside law firms will handle the litigation and have agreed to cover the up-front costs of the suit in exchange for a cut of potential monetary damages they get from the Raiders and the NFL.

Since early this year, local politicians, including Oakland council members Noel Gallo and Rebecca Kaplan, state Assemblyman Rob Bonta and Alameda County Supervisor Nate Miley, vocally supported the fan-driven lawsuit. But for a time it appeared to lack the necessary votes. Councilman Larry Reid, whose district includes the Coliseum property, had previously shown little interest in suing.

Kaplan declined to confirm if the city is moving forward with the suit. But, Kaplan, said, “I do believe, and have consistently advocated, that we should seek to protect Oakland taxpayers in dealing with the sports teams.”

A City Hall source said Mayor Libby Schaaf, who previously was on the fence about the lawsuit, was on board so long as the city’s legal fees were covered.

“The mayor’s office can not comment on anything that was discussed or may have been discussed in a closed session of City Council,” said Justin Berton, a spokesman for the mayor’s office.

Former Oakland Councilman Ignacio De La Fuente, a current Coliseum authority board member, said city leadership did little to keep the Raiders from leaving and called the lawsuit “ridiculous.”

“You are going to expose the city to potential liabilities and for what?” De La Fuente said. “You are trying to excuse yourself from not doing s— about it.”

De La Fuente, who as a councilman helped orchestrate the deal to bring the Raiders back in the 1990s, doubts the city would be protected in a counter suit, even with the outside law firms promising to front money for the first lawsuit.

“If you believe that, I will sell you the Brooklyn Bridge,” he said. “Once you are in, it’s very difficult to get you out.”

The news comes as the Coliseum authority, a board of county and city officials, is in negotiations to extend the Raiders lease. The team is leaving for Las Vegas, but the authority is in talks, which could be finalized as early as this month, to extend the lease for this season to next season, with an option for another year to play at the Coliseum. The rent to play in Oakland is expected to be doubled.

Coliseum authority Executive Director Scott McKibben said Tuesday, the Raiders “made it very clear to me that (if) they City decided to file a lawsuit they would not seek a lease extension to play at the Coliseum but would play elsewhere.”

The move is the latest in a saga over the Raiders’ stadium that has lasted years in Oakland, with attempts to move the team to Los Angeles, attempts to build a new stadium at the Coliseum site and with the ultimate vote last year by the NFL owners to allow the Raiders to relocate to a brand new 65,000 square-foot stadium in Las Vegas.

Last year, when fans brought the idea of a lawsuit to the authority, McKibben had cautioned against going the legal route. Instead, McKibben favored meeting with NFL executives directly to ask if the $200 million the league offered for the Raiders to stay could be used to help pay off the Coliseum debt.

Reached Tuesday, McKibben said he still would choose a path without litigation.

“It would be my recommendation that we approach the league with our case and concerns related to the debt,” McKibben said.

Oakland and Alameda County still owe about $75 million for stadium renovations made in 1996 to return the Raiders back to Oakland from Los Angeles. Under the deal with the Coliseum authority, the cost of renovations were to be paid with revenue from the sale of personal seat licenses, and the team was not obligated to pay the debt. The Golden State Warriors and the authority are currently in a battle over who should pay the debt from renovations at Oracle Arena.

Early this year, a fan group called “We Stand With Oakland” said at a news conference it had been contacted by law firms willing to file legal action against the team and the NFL to either keep the Raiders, get an expansion franchise or, if the team leaves, demand the league pay off the outstanding debt at the Coliseum. That came after a judge in Missouri made a ruling last year in favor of St. Louis officials suing the Rams for relocating to Los Angeles.

Staff writer Annie Sciacca contributed to this report.