A well-known bookmaker and the owner of three Washington D.C. professional sports teams plan to open the nation's first on-premises sports betting facility inside an arena.

In a partnership announced Thursday, betting company William Hill and Monumental Sports & Entertainment, which owns pro basketball and hockey teams in the nation's capital, said they would open a sports book inside Capital One Arena as soon as necessary approvals are obtained.

No estimated opening date was given, but signs at the arena indicate a 2020 opening is contemplated.

William Hill also will become the exclusive sports betting partner of the NBA's Washington Wizards, the NHL's Washington Capitals, and the WNBA's Washington Mystics.

Fans will be able to place bets at the sports book inside the arena, and also use a mobile app to bet inside the arena.

In a news conference Thursday, Joe Asher, president of William Hill US, said the sports book should engage fans more directly in the game, citing a hockey match from the night before when the Capitals were down early in the game.

"There would have been a lot of people betting on them to come back and win," he said. "And you get good odds when you're betting on the team that's behind to come back and win the game. So that just sort of drives further engagement. It gives people reason to watch more, to watch till the very end." (The Capitals won 3-2 in overtime).

The sports book will span multiple floors of the arena, and will be accessible to ticket holders and those without tickets. It will be open to accept bets on days when there are no events at the arena as well.

The companies envision broadcasting major out-of-area sports events on screens at the 20,000-seat arena, where fans could bet on them.

Several sports and lawmakers in numerous states have considered in-stadium wagering, but have not yet approved it. One version of a proposed sports betting bill New York legislators have been struggling with would allow betting in stadiums including Yankee Stadium and Citi Field.