Walgreens Boots Alliance has pumped the brakes on its planned $9.4B merger with Rite Aid due to continued antitrust concerns, the retailer announced Wednesday.

News that Krogers may no longer be interested in purchasing the 650 Rite Aid or Walgreens stores Walgreens was hoping to sell to appease antitrust regulators hit earlier this week, putting a snag in plans. Walgreens also announced it will likely have to close between 500 and 1,000 of its existing stores.

This new development means both retailers will need to find a competing retailer to take over their closed or consolidated locations to preserve competition in those areas, RetailDive reports.

Ever since the FTC shot down the Staples and Office Depot merger back in May, companies considering a merger have been working overtime to ensure they aren’t overconsolidating a sector. Walgreens is hopeful the deal will close in early 2017. [RD]