Amazon.com Inc. has filed a lawsuit challenging the Pentagon’s award of a $10 billion cloud contract to arch-rival Microsoft Corp., the latest twist in a months-long dispute over the coveted deal.

The company AMZN, +2.49% filed the suit in the U.S. Court of Federal Claims, a week after it indicated it would formally protest the government’s decision and suggested the contract for the Joint Enterprise Defense Infrastructure project, known as JEDI, was awarded based on political motivations. The powerhouse Amazon Web Services was once considered a shoe-in for the deal, in part because it had built cloud services for the CIA and it is the market leader.