Leaders of the effort to nail down a $900-million financial package for a new Tampa Bay Rays stadium in Ybor City say the outlines of a deal can still be reached before a Dec. 31 deadline.

But no binding documents have been inked. And as Hillsborough officials and the Rays parry, people on both sides now acknowledge that at the very least, the first pitch at a new ballpark might be delayed until 2024 — a year later than what had been proposed.

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St. Petersburg Mayor Rick Kriseman hasn't said what he'll do on Jan. 1, when a memorandum of understanding between his city and the team that allowed it to explore Hillsborough stadium sites expires. But any extension could cost the Rays millions.

The St. Petersburg City Council would have to approve it and one council member, Charlie Gerdes, has already suggested the city could force the team to pay up to keep talking to Tampa. Resolving that issue alone could delay construction, adding millions to a stadium price tag already pegged at $892 million.

The Rays aren't talking, but Hillsborough County Commissioner Ken Hagan, one of the leaders of Tampa's effort, said a finalized deal might not materialize until March.

"Ideally," Hagan said when asked if he'd like certainty by spring.

"The concern is the longer that it goes to reach an agreement,'' he said, the more likely Opening Day gets pushed back and construction costs go up.

"That's the fear,'' the county commissioner said.

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Ron Christaldi, who co-founded Rays 2020, the group responsible for signing up companies to spend millions on sponsorships, suites and other amenities, said progress may have slowed recently but the dream of Ybor City baseball is far from extinguished.

"Until it's dead, the deal is not dead," Christaldi said Thursday. "It's not dead until the Rays have contracted legally to another area."

Christaldi and Hagan said they take Rays principal owner Stu Sternberg at his word that the team doesn't have plans to skip out on the nation's 11th-largest television market for Portland, Ore. (where the city announced a ballpark site on Friday), Charlotte, Las Vegas, Montreal or Nashville — all cities rumored to be interested in landing a team.

Navigating the concerns of both sides is Irwin Raij, a New York attorney hired by Hillsborough County to function essentially as a go-between. Raij specializes in putting together professional sports stadium deals.

Hagan said the county and city haven't engaged in any direct negotiations with the Rays, a point confirmed by Raij in an email to the county attorney this week.

The Times asked Raij for comment about the negotiations, but he said he needed to get permission from county officials first. He did not call back.

So what are the stumbling blocks?

Money. The Tampa group would like the Rays and any private investors they can persuade to invest in the project to shoulder at least half of the stadium's cost, or about $450 million.

"It's always been assumed the team would have to invest at least half of the cost," Hagan said.

Sternberg has said the team would be willing to contribute around $200 million if enough corporate support materializes, including money for the right to name the ballpark.

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While naming rights discussions have picked up, Rays executives have remained silent about how much more the team is willing to fork over to build a state-of-the-art ballpark with a translucent roof in the heart of historic Ybor, one of the oldest and, arguably the most storied neighborhoods in Tampa Bay.

What Hagan, Christaldi and others would really like to have finished by the end of the year is a non-binding agreement outlining in general terms what is expected from taxpayers and local governments in Hillsborough County.

Those terms may include:

• Taking dollars from property tax revenue earmarked for community redevelopment for street, utility and landscape improvements and using a portion of the county's tourist bed tax revenue.

• Creating a Community Development District that would levy an annual assessment on property owners within the district.

• Encouraging investment in the Opportunity Zone there, created as part of the 2017 federal tax cut legislation to help low-income areas by allowing investors to avoid paying taxes on profits earned elsewhere for up to 10 years. Opportunity Zone investment could raise millions, experts have said.

Hagan said investors are already lined up but declined to identify or discuss them, other than to say they were investment firms.

A memo sent by County Administrator Mike Merrill to commissioners on Friday provides even more detail about the deal that county officials hope the Rays will accept.

It says the Rays, the city of Tampa and Hillsborough County may each have to put up a reimbursable guarantee not to exceed $50 million.

The team would be required to pay for any construction cost overruns and to make annual rent payments. The Rays would also have to pick up the tab for stadium repairs, maintenance and future ballpark upgrades.

Like Raymond James Stadium, Amalie Arena, and Steinbrenner Field, the memo states, the baseball stadium would not be subject to property taxes except for private sections controlled by the Rays.

That framework is intended to form the basis for upcoming negotiations — although it's unknown if that framework is acceptable to the Rays.

If an agreement is reached, a "term sheet" would be presented to the county commission, the Tampa City Council and the Tampa Sports Authority no later than April 30.

"If approved by all parties, (it ) would be binding and would trigger the drafting of detailed transaction documents that would be approved by the parties," the memo states.

Other areas of negotiation could include details of financing and the length of debt obligations, Christaldi said.

He said failing to make the end-of-the-year deadline doesn't give him too much angst.

"I don't see that in my mind as a significant setback," Christaldi said.

If those general principles can be ironed out, Hagan said the Rays' history in the Sunshine City will come to an end after two decades.

"All of this would give the Rays the comfort they need to tell St. Pete they're going to Tampa," Hagan said.

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Across the bay this week, Kriseman was highly critical of Hagan's role in the process, calling for him to recuse himself after a 10News WTSP story suggested that Hagan and Blue Pearl CEO Darryl Shaw colluded on land purchases within the selected stadium footprint north of Adamo Drive, near the Ybor Channel.

Hagan has denied the allegations. He asked the county attorney to research a possible defamation suit against the reporter and to prepare a memo to other commissioners that would exonerate himself and Shaw through public documents.

On Thursday, Kriseman spokesman Ben Kirby said the mayor remains concerned about Hagan's involvement.

"Mr. Hagan has proven to be disruptive throughout this process," Kirby texted to a Times reporter.

The 10News stories, which also revealed that Shaw had loaned $1.5 million to the Times in 2016, were a "side note right now," said Christaldi, who said he didn't think they damaged trust between the parties or poisoned public perception of the ballpark talks.

"I haven't seen anything that gave me concern," he said.

Hagan said he had no plan to step away from his lead role, which may be discussed at Wednesday's County Commission meeting. He said he remained confident that baseball won't abandon Tampa or the Tampa Bay region.

Still, he said more work needs to be done.

"While we've made progress, we're not there yet," he said.

Contact Charlie Frago at cfrago@tampabay.com. Follow @CharlieFrago. Contact Christopher O'Donnell at codonnell@tampabay.com or (813) 226-3446. Follow @codonnell_Times.