The two companies are left in the fray for the lucrative contract after Alphabet Inc Google dropped out on Monday, saying the company's new ethical guidelines do not align with the project.

Pentagon's JEDI, or Joint Enterprise Defense Infrastructure, cloud computing solution contract is part of the Department of Defense's efforts to modernize its IT infrastructure.

The expanded Azure Government Secret cloud service will make Microsoft "a strong option for the JEDI contract," said Julia White, corporate vice president of Microsoft Azure, adding that the company is capable of meeting the highest classification requirement for handling "top secret U.S. classified data".

(Reporting by Akanksha Rana in Bengaluru and Jeffrey Dastin in San Francisco)