OAKLAND — Just as the Golden State Warriors set out to defend their NBA title, a legal defense is ramping up over how much the team will owe for improvements made to Oracle Arena once the franchise makes its planned move to San Francisco.

Lawyers for the Warriors, in an Oct. 6 letter to the American Arbitration Association, argue that the team has no obligation to pay any remaining debt once it leaves Oakland.

The arena’s operator, the Oakland-Alameda County Coliseum Authority (OACCA), contends the team must pay all the remaining debt — estimated to be about $40 million — regardless of where it plays.

The Oct. 6 letter was the Warriors’ first public filing on the matter and sets the tone for what could be a prolonged legal battle between the two sides.

If a requested mediation does not work, the dispute will head to a third-party arbitrator. If an arbitrator rules in the team’s favor, the arena’s operator, the publicly run Coliseum authority, could be responsible for the remaining debt when the Warriors leave. The team intends to play in an arena it is building in San Francisco beginning with the 2019-20 season.

The dispute is over the language of a 20-year lease signed in 1996 that included upgrades to the arena. The lease specified that the team would make annual payments on the debt and be responsible for the debt if it terminated the lease. At the time, the Coliseum authority issued $140 million in bonds to renovate the arena, work that included gutting the interior. A new two-year lease signed last year contains the same language.

Each year, the Warriors have paid $7.4 million from premium seat revenues toward the bond debt, which will leave the debt at $40 million if the team leaves Oakland in 2019 and $32 million should they play an additional year.

Attorney Joshua Hill, in the Oct. 6 letter, argued that the language of the contract requires the Warriors to pay the remaining debt if the team terminates its lease early, but does not if the team plays at the arena until the lease expires on June 30, 2019.

“The reality is the OACCA will continue to own and have the right to operate Oracle Arena after the license agreement expires and, as dictated by the license agreement, the OACCA will then bear sole responsibility for the scheduled debt service,” according to the arbitration and mediation demand. “This predicament is entirely of the OACCA’s own making, as it bargained for a 20-year term in the license agreement while issuing 30-year bonds.”

The team issued a statement late Wednesday saying that it is seeking arbitration “to settle, once and for all,” the outstanding debt.

“Since purchasing the team in 2010, the new ownership group immediately paid some $10 million that were in dispute between the Coliseum Authority and the prior ownership group, invested many millions of dollars more in a new scoreboard and other upgrades to the arena, and more recently negotiated a lease extension with an increased annual rent payment to ensure that the team will play its next two seasons at Oracle Arena,” the statement read.

It went on to say that “The Warriors are hopeful that this dispute can be resolved through mediation. But, whether resolved by mediation or arbitration, the simple fact is, the team has met its obligations under the lease, and future debt payments following expiration of the contract are the responsibility of the arena’s owner and operator, the Coliseum Authority.”

Alameda County Supervisor Nate Miley, who serves as the president of the authority board, declined to comment through his communications director. The authority board is scheduled to discuss the issue in closed session at its Friday meeting.

Coliseum authority Executive Director Scott McKibben stood firm on the authority’s position.

“We believe it’s clear that the Golden State Warriors owe us the balance of the total project debt, which is the entire bond,” McKibben said Wednesday.

By contrast, the Oakland Raiders are not obligated to pay for the renovations to the Coliseum made to lure the team back in 1995. The Coliseum debt stands at $83 million.

“I think it’s incredibly inappropriate for (the Warriors) to be threatening not to pay the full amount they owe,” Oakland Councilwoman Rebecca Kaplan said last month. “The people of Oakland are struggling, and this is the public’s money. I would hope they care enough about their reputation that they wouldn’t want to be seen as a deadbeat.”