Amazon.com Inc. is turning to the debt markets to fund the acquisition of Whole Foods Market Inc. and power Jeff Bezos's planned conquest of the supermarket business.

The world's largest online retailer is selling unsecured bonds in as many as seven parts, according to a person with knowledge of the matter. The longest portion of the offering, a 40-year security, may yield 1.6 percentage points to 1.65 percentage points above Treasuries, said the person, who asked not to be identified as the deal is private.

Amazon is offering bonds for the first time since 2014 to support the $13.7 billion purchase of the organic-food chain, according to a company statement, a deal that rattled the grocery world in June. The partnership is expected to reduce prices at Whole Foods, an iconic yet struggling high-end grocery trying to lure more low- and middle-income shoppers. The deal could intensify a price war in an industry beset by razor-thin margins and persistent deflation.