ATLANTA — Atlanta Mayor Andre Dickens has agreed to sell the Atlanta City Detention Center to Fulton County for $68 million.

Dickens told the Fulton County Commission chair that the purchase will ultimately make more money than it costs.

In a letter to the commission chair, Dickens wrote that the deal could bring more than $600 million to taxpayers by leveraging existing capacity, avoiding greater capital costs, protecting employees and keeping detention center operations.

The agreement follows weeks of negotiations over the future of the facility. Fulton County previously offered $56.5 million before that offer expired without a deal, prompting Atlanta to raise its asking price.

The county later agreed to the $68 million price, but negotiations continued over a condition that would have required Fulton County to commit $200 million toward construction of a new hospital on Atlanta’s Southside, officials said.

Officials previously said Fulton County is already using the detention center to house inmates under a lease agreement with the city and that lease was set to expire at the end of the year.

Still, the proposal has opponents. Activist Devon Barrington Ward warned against the sale.

“We are on the precipice of having one of the largest jail systems in the county if you sell this building to Fulton County. Let my words be a warning. History will be the judge,” Ward said.

Fulton County currently leases space at the detention center to house inmates. That lease is set to expire at the end of the year.