The National Security Agency has quietly awarded a contract worth up to $10 billion to Amazon Web Services, setting off another high-stakes fight among rival tech giants over national security contract dollars.

On July 21 the Redmond, Wash.-based Microsoft filed a formal bid protest with the Government Accountability Office, an independent federal agency that handles contract disputes, after Microsoft applied for the opportunity and was rejected. A decision is expected by Oct. 29.

The contract award comes on the heels of a protracted and bitter dispute over a Pentagon contract, also worth up to $10 billion, which was given to Microsoft before getting bogged down in lawsuits and ultimately scrapped. If the NSA can fight through an often bruising bid protest process, the new contract could extend Amazon’s lead in the fast-growing cloud computing market where rivals are gaining on it.

The NSA has offered few details about the purpose of the contract. An NSA spokesman said the agency had awarded a contract for “cloud computing support services,” but declined to elaborate or specify who won it. “The agency will respond to the protest in accordance with appropriate federal regulations,” the spokesman said.

Two people with direct knowledge of the contract, speaking on the condition of anonymity to discuss proceedings that haven’t been made public, confirmed that Amazon is the awardee, and that the maximum value of the cloud deal is $10 billion. Amazon’s receipt of the contract was first reported by Washington Technology and later confirmed by NextGov. Both are trade publications focusing on military technology and procurement issues. Both publications said the contract carries the code name “WildandStormy.”

A Microsoft spokeswoman confirmed the company has protested the NSA’s decision. “We are exercising our legal rights and will do so carefully and responsibly,” the spokeswoman said. An Amazon spokesman referred questions to the National Security Agency.

Amazon founder Jeff Bezos owns The Washington Post.

The NSA’s decision to award such a large contract to a single company is sure to stir up controversy in a national security ecosystem where large deals with big tech companies have occasionally been fraught with allegations of bias and undue influence.

“Any time you have these large contracts with hundreds of millions of dollars in spending, without much knowledge of the competition, it draws intense scrutiny. … It just depends on whether the agency can withstand that scrutiny,” said Alan Chvotkin, a government contracts attorney with the law firm Nichols Liu.

The Defense Department recently pulled the plug on a different long-planned cloud computing award after years of bid protests and dueling allegations of corruption. That contract, the Joint Enterprise Defense Infrastructure, or JEDI for short, was given to Microsoft shortly after former president Donald Trump took interest in the procurement. There are also allegations that Amazon had an unfair advantage due to its relationships with federal officials.

The NSA award is likely to improve Amazon’s prospects in the insular national security sector, where untold billions in spending from the Pentagon and the intelligence community represent a lucrative growth market.

The e-commerce giant has been making inroads there for years. It got an early foothold in 2013 when it secured a $600 million cloud contract with the CIA. That work accelerated Amazon’s capabilities with respect to handling classified and top secret data, while also allowing other government agencies to access its services.

Microsoft’s surprise 2019 JEDI win upended the federal IT world and, for a time, allowed Microsoft to say it was the U.S. military’s favored cloud provider. Microsoft had already been gaining on Amazon; updating its technology with defense work in mind, and obtaining new security clearances required for sensitive national security work.

Amazon’s bid protest ultimately halted Microsoft’s progress, as a protest-weary Pentagon opted to start a new procurement open to both companies. AWS also won a seat on a different intelligence community contract, estimated to be worth tens of billions of dollars, that was given jointly to five major cloud providers.

The nature of the NSA’s work makes it hard to determine what sort of business, if any, Amazon has with the famously secretive agency. Last year the company added Keith Alexander, a former NSA director who is influential in the cybersecurity industry, to its board.

John Weiler, a former Oracle employee who now works with the IT Acquisition Advisory Council, said the NSA’s strategy bears an unfortunate similarity to the Pentagon’s JEDI contract.

“Amazon is still sitting as the dominant force in government cloud, but Microsoft had preexisting monopolies of its own,” Weiler said. “You have two monopolists fighting to dominate a market that is very rich and very large.”