SAN FRANCISCO (REUTERS ) - Amazon on Friday filed a lawsuit in the US Court of Federal Claims contesting the Pentagon's award of an up to US$10 billion (S$13.6 billion) cloud computing contract to Microsoft.

An Amazon spokesman said that the company filed a complaint and supplemental motion for discovery. The filing was under seal.

"The Complaint and related filings contain source selection sensitive information, as well as AWS's proprietary information, trade secrets, and confidential financial information, the public release of which would cause either party severe competitive harm," Amazon said in a court document seeking a protective order.

"The record in this bid protest likely will contain similarly sensitive information."

Last week, US Defence Secretary Mark Esper rejected any suggestion of bias in the Pentagon's decision to award Microsoft the contract after Amazon announced plans to challenge it.

Amazon was considered a favourite for the contract, part of a broader digital modernisation process of the Pentagon, before Microsoft emerged as the surprise winner.

The company has previously said that politics got in the way of a fair contracting process. US President Donald Trump has long criticised Amazon and its founder Jeff Bezos.