ST. LOUIS (AP) The proposed riverfront stadium in St. Louis has a naming rights deal worth $158 million that hinges on the city having an NFL team when the facility opens.

National Car Rental has reached a 20-year agreement with the St. Louis Regional Sports Authority for what will become ''National Car Rental Field,'' officials with the stadium task force and National told The Associated Press on Tuesday. But the stadium is no sure thing and wouldn't open until 2019 at the earliest.

The company, a unit of St. Louis-based Enterprise Holdings, will pay $6.5 million in the first year, with a 2 percent annual inflation escalator every year after that. The agreement calls for interior and exterior signage. The money will go either to the team owner or the sports authority, depending on what agreement is ultimately reached, said Dave Peacock, co-leader of the stadium task force appointed by Gov. Jay Nixon.

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Peacock said the deal is ''a testament to both the positive business climate you're going to see for St. Louis and NFL football, and it's also a strong message from a great company in our city and a great family who owns and runs that company that they're continued support of St. Louis is remarkable.''

Patrick T. Farrell, chief marketing and communications officer for Enterprise Holdings, said the company has worked hard to upgrade the National Car Rental brand since purchasing it in 2007.

''The National Football League aligns very closely, almost identically, with the demographic target for the frequent renters that use the National brand,'' Farrell said.

It's still unclear if St. Louis will have an NFL team when the stadium is finished. Rams owner Stan Kroenke is seeking to move to Los Angeles. He is part of an effort to build a new stadium in Inglewood, California.

Owners of the San Diego Chargers and Oakland Raiders want to move, too, and are combining on a stadium project for Carson, California. The NFL hasn't had a team in Los Angeles, the nation's second-largest market, since the Rams and Raiders left in 1995.

Owners are meeting this week in New York, and franchise movement will be among their talks, but a decision isn't expected until early next year.

The Rams' current home, the Edward Jones Dome, was built completely with taxpayer funds, opening in 1995. Two decades later, the dome is outdated by NFL standards. Efforts between the Rams and the agency that operates the dome to broker an upgrade went nowhere.

The St. Louis stadium proposal was announced in January. Bond extensions would provide $201 million for the new open-air, 64,000-seat stadium sitting directly along the Mississippi River, just north of the Gateway Arch. A combination of seat licenses, state tax credits and other incentives would help pay for it. About half the money likely would come from the team owner and an NFL loan program.

Enterprise Holdings is the world's largest car rental company. In addition to National, it operates the Enterprise Rent-A-Car and Alamo Rent A Car brands. CEO Pamela Nicholson said the naming rights for the hometown company mean more than marketing and advertising.

''It's about playing our part in a historic effort to renew our riverfront, further revive our downtown area and reinforce St. Louis's standing as a truly great city,'' she said in a statement.

Stadium task force leaders say the venue could also serve as a home for Major League Soccer and host concerts and other events.