Microsoft Corp. scored a major victory in securing a milestone, $10 billion Pentagon contract for cloud computing services. But the contract — unthinkable for Microsoft even a year ago — will likely come at a cost, legal and internal.

Amazon.com Inc., the market leader in cloud services, is considering a challenge to the award of the contract to Microsoft's much smaller Azure business, citing President Donald Trump's interference in the bidding process, according to a person familiar with the matter. Amazon had been widely considered the front-runner because of its superior size and previous cloud contract with the Central Intelligence Agency.

Meantime, Microsoft employees have protested involvement in the contract, known as the Joint Enterprise Defense Infrastructure, or JEDI, intended to bring U.S. military technology into the modern era.