Kansas City, Mo. ? A Los Angeles-based sports and entertainment firm signed an agreement Thursday to contribute $50 million toward construction of a proposed downtown arena, city and corporate officials announced.

The agreement commits Anschutz Entertainment Group to covering construction cost overruns, absorbing any operating deficits for 35 years and working to bring a National Hockey League or National Basketball Association team to the city.

AEG’s contribution hinges on voter approval Aug. 3 of proposals to add $1.50 to the city’s daily fee on hotel room occupancy and $4 to the daily fee on rental cars. The fees would raise an estimated $123 million toward construction costs, expected to total $225 million to $250 million.

“Hopefully, this agreement we are announcing today will create some comfort for the citizens of this city that Kansas City is clearly protected from cost overruns, operating loses and event risks,” Tim Lieweke, president and chief executive of Anschutz Entertainment, said at a news conference with Mayor Kay Barnes.

The balance of the construction costs would come from user fees, tax credit financing, the sale of naming rights to Sprint Corp. and $10 million from the National Association of Basketball Coaches, which wants the 18,000- to 20,000-seat arena to house a National Collegiate Basketball Hall of Fame.