Amazon (AMZN 2.50%) has agreed to acquire as many as 5.4 million shares of SpartanNash (SPTN 0.38%), or 15% of the food distribution leader's total outstanding stock, as the e-commerce giant wades further into the grocery business.

SpartanNash disclosed in a regulatory filing Thursday that as part of a commercial agreement with Amazon, it was issuing warrants to the e-tailer of which more than 1 million would vest immediately, with the rest able to be purchased over the next seven years.

Woman shopping in the produce aisle

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Express lane to growth

The pact comes as Amazon looks to expand its new Fresh grocery store chain that's part Whole Foods, part Amazon Go, and part 365, the discount grocery store it closed last year. Fresh incorporates a mix of organic, premium, and low-priced national brands; cashier-free checkouts; and online fulfillment through curbside pickup.

SpartanNash distributes groceries to independent supermarkets, military commissaries, and its own chain of stores, but it has also had a relationship with Amazon since 2016 when it agreed to supply the e-commerce leader's distribution centers with groceries.

Dollar General is currently SpartanNash's largest customer, representing 17% of the food distributor's $8.5 billion in annual sales, while Amazon's existing business accounts for less than 10% of the total. The new agreement, though, could see Amazon's contribution increase significantly and taking an ownership stake in its partner is reminiscent of the stakes it took in aircraft leasing companies Air Transport Group and Atlas Air Worldwide.

Earlier this year Air Transport issued warrants for up to 33% of its stock and Atlas up to 40% based on the number of aircraft Amazon leases. If Amazon hits certain performance targets with SpartanNash, it could become the second largest shareholder in the company.