DEERFIELD, Ill. — Walgreens Boots Alliance (WBA) said it’s working on store divestiture scenarios with the Federal Trade Commission to gain clearance for its $17.2 billion deal to acquire Rite Aid Corp.

WBA said Thursday that it and Rite Aid “remain actively engaged” in talks with the FTC as the regulator reviews the acquisition, which was announced on Oct. 27.

“As a result of the progress of these discussions with the FTC staff, Walgreens Boots Alliance is exploring potential divestiture remedies to address certain issues raised in those discussions,” WBA said in a statement.

Updating its previous estimate, WBA said it now appears that more than 500 Walgreens and/or Rite Aid stores will need to be divested, but the company “still continues to expect that fewer than 1,000 stores will be required to be divested.”

“In addition, the company continues to believe that the acquisition will close in the second half of calendar 2016,” WBA stated.

WBA has previously indicated that it’s willing to divest up to 1,000 stores to gain regulatory approval but expects divestitures to be less than half that number. Together, Walgreens and Rite Aid would create the largest U.S. chain drug retailer, with more than 12,700 stores.

In reporting third-quarter results on July 6, WBA said the Rite Aid acquisition is “progressing as planned” and that WBA “is continuing its integration planning.” And in a conference call that day, WBA executive vice chairman and chief executive officer Stefano Pessina told financial analysts, “We still believe that our initial estimate is correct. We still believe that at the end we will stay in the range of the stores [to be divested] that we initially indicated, around 500.”

Also on Thursday, WBA said it expects the acquisition to be accretive to its adjusted earnings per share in the first full year after the deal is finalized, based on its current outlook for store divestitures. The company added that it continues to expect acquisition synergies of over $1 billion, which would be fully realized within three to four years after the transaction is completed.

“These synergies have been updated where practicable and, as previously disclosed, are expected to be derived primarily from procurement, cost savings and other operational matters,” WBA said.