Apple rarely disputes reports of its interactions with foreign governments, but the company spent the weekend actively denying last week’s Bloomberg story that alleged it has known since 2015 that China inserted spying chips into Supermicro servers used for cloud services. Reuters reports that Apple VP George Stathakopoulos contacted the U.S. Congress on Sunday to reiterate that the company has never found malicious chips or vulnerabilities in any server, nor been contacted by the FBI regarding the issue, claims made in the Bloomberg report.

While Apple, Supermicro, and Amazon all disputed the key elements of Bloomberg’s report, Apple has been particularly aggressive in its efforts to deny the claims. Though Bloomberg said its story was based on 17 sources, Apple told Congress it believes some of the allegations were based on fewer sources — a standard reporting technique — and in some cases came from only a single source.

Bloomberg has stood by its story, which it worked on for at least a year before publication. It claimed that Chinese spies placed tiny chips on Supermicro’s motherboards, enabling the spies to compromise the servers for information-gathering purposes and then keep them awaiting further instructions. It further claimed that Apple and Amazon became aware of the issues and reported them to the FBI, quietly assisting in an investigation that has been ongoing since 2014.

The story has potentially profound global ramifications. If true, it suggests China’s government employed a particularly invasive and challenging spying technique against U.S. targets. Additionally, it could disrupt U.S. reliance upon Chinese manufacturing and supply chains — the key to device-building strategies employed by Apple, Amazon, and many other companies. And it could undermine Apple’s relationship with the Chinese government, which the company has carefully cultivated over the last five or so years.

Because of the shadowy workings of national and international security agencies, it’s virtually impossible for any company — or even any government — to truly refute Bloomberg’s claims. Spy agencies and their collaborators do not generally admit to clandestine activities, and denials can range from carefully parsed to outright lies, depending on the actors and specifics of operations.

That said, Apple’s denials have been broad and emphatic, with the company arguing that the story’s details — specifically regarding Apple — were substantially if not completely incorrect. Apple’s position is bolstered somewhat by the U.K.’s National Cyber Security Centre and U.S. Department of Homeland Security, both of which have issued statements saying that they have no reason to doubt Apple’s or Amazon’s denials regarding spying chips. Apple also allowed its former top lawyer, Bruce Sewell, to talk with Reuters regarding his discussions with the FBI a year ago, when Bloomberg initially reached out for comment on the allegations.

Apple is expected to continue its full court press this week, as Stathakopoulos will be offering briefings to Congressional staff regarding the company’s position. It’s uncertain whether Bloomberg will respond to the mounting challenges to its reporting.

Update at 8:56 a.m. Pacific: The full Apple letter, including its denials of the story and specific affirmations of the broader global implications of the allegations, has been posted to Scribd. “If any of the reported details were true,” Stathakopoulos told Congress, “we would have every interest —economic, regulatory, and ethical — to be forthcoming about it.”