Atlanta may have to come up with a lot more cash if it wants to secure the proposed site for a new stadium for the Atlanta Falcons.

Friendship Baptist Church, one of two churches sitting on sites proposed for the stadium, has rejected a $13.5 million offer for its building and property, Atlanta officials have confirmed.

Mayor Kasim Reed, in an exclusive interview with 11 Alive news, said the church entered a counterproposal of $24.54 million.

“We can’t afford that, so we sent back an offer of $15.5 million,” Reed told the TV station.

This marks the first time a dollar figure has been made public, giving a glimpse at what it might take to secure one of the churches. Plans for a $1 billion retractable-roof stadium to replace the Georgia Dome call for both Friendship and Mount Vernon Baptist to be demolished.

Neither property has been appraised by representatives of the project. Fulton County tax records show Friendship’s property is worth more than $1.2 million and Mount Vernon’s tops $1 million.

Friendship Baptist officials could not be reached for comment, and church leaders have been largely mum as negotiations have been under way. The city and church have an August 1 deadline to strike a deal.

Meanwhile, the state is negotiating with Mount Vernon Baptist to buy its land. The Georgia World Congress Center is leading those negotiations, and no dollar figure has emerged on what it might take to procure Mount Vernon.

Backers of the retractable-roof field want it at Martin Luther King Jr. and Northside drives, making both church sites valuable to where the stadium will sit and how the public will access it.

Under terms outlining the stadium project among the Atlanta Falcons, the city and the Georgia World Congress Center Authority, if there is no deal to secure the church properties at the end of July, the Martin Luther King Jr./Northside location — known as the “south site” — will be abandoned and the stadium’s construction will automatically shift almost a mile north of the Dome to Ivan Allen Jr. Boulevard near Northside Drive.

There has been opposition to leaving both buildings, most vocally at Friendship. Juanita Jones Abernathy, widow of civil rights icon the Rev. Ralph David Abernathy, has been a vocal opponent of a sale, saying the 151-year-old church has too much historical importance to be leveled, including being the site of the early classes of Spelman and Morehouse colleges.

In the preferred plan, the stadium would be constructed where Mount Vernon currently sits, while Friendship would be demolished to allow Martin Luther King Jr. Drive to be moved west into a curve to give the new stadium a bigger footprint.

The Falcons and local leaders agreed to funding terms earlier this year for a new stadium that will require the Falcons to pick up 80 percent of the stadium’s cost while about $200 million in city hotel-motel tax collections will fund the remaining expenditure.