OAKLAND — The proposed deal to have the Raiders play one final season in Oakland could unravel, the Coliseum Stadium Authority warned Wednesday morning, adding another layer of intrigue to the saga over where the wayward team will land before its new $1.9 billion home is ready in Las Vegas.

While stadium authority Executive Director Scott McKibben said the deal is “95 percent there,” he said the sides are stuck on one issue, and it’s possible the Raiders and the Coliseum won’t be able to come to an agreement before Tuesday’s deadline. McKibben wouldn’t reveal details of what he called the “significant” remaining issue, but sources say it relates to the team’s training facility and headquarters in Alameda.

The Raiders brought the issue to McKibben’s attention on Friday, a setback after officials said talks were progressing. Team executives did not return messages sent Wednesday.

“This could very likely put us in a position where there’s not a deal,” McKibben said after a closed-session meeting in which he updated his board on the negotiations. “It’s going to be one of those, ‘Yes, we (the Raiders) are willing to try and resolve this,’ or, ‘No, we feel firmly about this and we are not going to do it’ (and) the deal blows up.”

BREAKING: Coliseum stadium exec says Raiders deal is 95% there but it’s possible it could unravel if one “significant” issue is not resolved. The Raiders brought the issue to Executive Director Scott McKibben on Friday, per McKibben. pic.twitter.com/bEnMOVB8RC — David DeBolt (@daviddebolt) March 6, 2019

The Raiders have essentially agreed to a deal that would have them paying $7.5 million in rent to play in Oakland in 2019. If the team stays in 2020, rent jumps to $10.5 million. That’s triple what the team paid last season.

McKibben said there was agreement on most terms, and he insisted the sticking point wasn’t related to rent, the Coliseum’s retention to all stadium naming rights, or that the Oakland City Council’s lawsuit against the Raiders and NFL. A source familiar with negotiations said the snag involves finances and taxes related to the team’s headquarters and training facility. As part of the lease agreement, the team pays $525,000 a year in rent for the practice facility and is allowed to continue using it for 36 months after the Raiders relocate to Las Vegas.

McKibben said he’d speak with Raiders owner Mark Davis and team president Marc Badain as soon as possible to discuss the Coliseum Authority’s contract concerns.

There is a time element working against both sides as the NFL needs to know where the Raiders will play in 2019 so it can work out the league’s schedule. Commissioner Roger Goodell had said before he’d like the Raiders issue resolved at some point in February. NFL owners begin meetings March 24-27 in Phoenix.

In order to get a stadium deal approved by the city and the Coliseum Authority by next Friday , McKibben said the undisclosed issue needs to be resolved by Tuesday morning, at the latest. Once the stadium board approves the lease extension, it moves to votes of the Oakland City Council and Alameda County Board of Supervisors.

McKibben confirmed that the Raiders’ rent would be higher than they’ve ever paid, resulting in net revenue of $2 million to $2.5 million a season. Under previous deals, the city and county, which own the Coliseum, lost about $1.7 million in revenue hosting Raiders games.

“This will be probably the best financial deal for the taxpayers in terms of a tenant lease relationship that we’ve ever had here,” McKibben said.

Currently, the city and county are on the hook for $75 million in Coliseum debt, which stems from renovations to lure the Raiders back to Oakland in 1995. Sales of personal seat licenses were supposed to pay for the debt but not enough were sold and the money never materialized. The Raiders have no obligation to pay the debt, and it never included the Oakland A’s.

Davis backed out of negotiations in December after the Oakland City Council filed an antitrust lawsuit against the team, NFL and the league’s owners over the Raiders relocation to Las Vegas. After two months of unsuccessfully searching for a new home, including the San Francisco 49ers home at Levi’s Stadium in Santa Clara, and Oracle Park in San Francisco, where the San Francisco Giants play, the Raiders returned to talks with Coliseum officials. McKibben said the Raiders have “accepted the fact that the Oakland lawsuit is going forward.”

“That is not an issue, we are past that,” he said.