Amazon filed a lawsuit in a federal U.S. court on Friday contesting the U.S. Defense Department¡¯s decision last month to award a Pentagon cloud computing contract worth up to $10 billion to rival bidder Microsoft.

The complaint and supplemental motion for discovery were filed in the U.S. Court of Federal Claims under seal, according to a spokesman for Amazon Web Services, a division of the online retail giant founded by billionaire Jeff Bezos.

The company did not explain the basis for its complaint.

The filings contain ¡°proprietary information, trade secrets, and confidential financial information¡± that could ¡°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,¡± it said.

The previous week, U.S. Defense 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.

¡°We believe the facts will show they (DoD) ran a detailed, thorough and fair process in determining the needs of the warfighter were best met by Microsoft,¡± Microsoft said in an emailed statement.

Amazon had been considered a favorite for the Joint Enterprise Defense Infrastructure Cloud (JEDI) contract, part of a broader digital modernization project at the Pentagon, before software developer Microsoft emerged as the surprise winner.

Amazon has previously said that politics got in the way of a fair bidding process. Bezos, the chief executive officer of Amazon and owner of the Washington Post, has been an outspoken critic of U.S. President Donald Trump.