A proposed half-billion dollar overhaul of the Phoenix Suns' home court faces opposition from the two leading candidates for Phoenix mayor.

You haven't heard much about this deal because it's being hammered out behind closed doors.

The Phoenix City Council has met in executive session for several weeks to discuss the proposed renovation of the city-owned Talking Stick Resort Arena. No information has been released, and negotiations are continuing.

12 News has learned the renovation of the 25-year-old arena would cost about $450 million, with taxpayers kicking in $225 million, largely from proceeds of the recent sale of the city-owned Sheraton Grand Phoenix downtown.

The Suns' contribution is unclear, though one source familiar with the plan said the team would spend at least $125 million.

The plans do not include a hockey rink for the Arizona Coyotes.

The first public comment on the arena talks came this week, when the two leading candidates for Phoenix mayor voiced their opposition, potentially dooming the project.

Councilwoman and mayoral candidate Kate Gallego issued a statement Wednesday saying she wouldn't spend taxpayer dollars on a new or improved arena for the Suns:

"The city of Phoenix has a strong relationship with the Phoenix Suns that has benefited both the city and the team. I do not believe though that Phoenix should invest in either a new or improved arena for the Suns. We have a number of competing priorities and tough choices we have to make if we're going to fuel our growth and build on recent progress in Phoenix. While I intend to be a partner with the Suns on the many great things they do for the city, it is not in Phoenix's best interest to invest in an arena."

A few hours later, after being asked for comment by 12 News, Councilman Daniel Valenzuela, Gallego's opponent, issued a statement indicating he agreed with her:

"For too long, taxpayers have been expected to foot the bill for sports venues. This practice must stop now. Hosting the Suns, concerts and other high-profiled events at our arena is critical to our downtown and its economic vibrancy. As leaders, we need to bring stakeholders together to develop a new model that takes the burden off our taxpayers."

Valenzuela's public opposition came as a surprise to other council members, who had assumed he was supporting the deal.

"It gets harder to do (the deal), particularly with as divided a council as we tend to be," said Councilman Jim Waring, who plans to vote "no" on an arena deal.

The council is heading into 2018 facing several unknowns, with three of its nine members - Gallego, Valenzuela and Mayor Greg Stanton - expected to resign to run for higher office. Appointees would fill their seats.

The Suns have played at the arena since its opening in 1992. The team has an option to get out of its lease in 2022, by triggering an "obsolescence clause" in its lease within the next two years.

In July, team owner Robert Sarver said he preferred renovating Talking Stick over building a new arena.

“I think it’s the most economically viable alternative for the city and us,” he said in July. “I like downtown Phoenix. That’s my first preference. I think the NBA is more of an urban game. That’s our demographic.”

A renovation has the advantage of requiring only the City Council's approval, not a taxpayer vote. Construction of a new arena would require a citywide vote at a time when the Suns' fortunes have waned and taxpayers are weary of subsidizing pro sports teams.

The city commissioned a consultant's report last spring on the cost of renovating the arena for hockey or basketball.

12 News filed a public records request for the report several months ago. The city has denied the request, claiming the report was being used in confidential real estate negotiations.

The high price tag for the renovation, compared to the cost of new arenas in the NBA, indicates the project is more of a rebuild of the stadium interior.

The Milwaukee Bucks are building a new arena for $524 million. Sacramento’s new arena costs $560 million.

A Phoenix Suns spokesman declined to comment.

Mayor Greg Stanton couldn't be reached for comment.

The City Council is expected to discuss the Suns deal behind closed doors next week and could vote on it by the end of the year.