Microsoft has started private testing of its Windows Azure Government Cloud, its Azure variant specifically for U.S. government customers.

Microsoft announced plans for the Azure Government Cloud last October . That version, codenamed Fairfax, is Azure-hosted in Microsoft's data centers in Iowa and Virginia and managed by U.S. personnel, similar to the way Office 365 for Government is. (Fairfax, Virg., is the home of the General Services Administration, and close to other U.S. government agencies.)

At the time of the official unveiling, Microsoft officials said Azure Government Cloud would be "coming soon."

On March 3, Microsoft execs said they are now working with customers on "private previews" of the new service. Following these private previews, the team plans to open up a "limited public preview." Microsoft officials are not providing a date as to when Azure Government Cloud will be generally available.

"The Azure government cloud will have physical and logical isolation at all layers, it will be run by U.S. personnel with government background investigations and follow defense-in-depth, multi-level security practices," said Greg Myers, Vice President, Microsoft Federal, in a new blog post.

Currently, Microsoft sells the same set of Windows Azure and Windows Server offerings to government users, alongside all other types of users. But Microsoft already sells a version of its Office 365 hosted app platform that's customized for government. Office 365 for Government is a multi-tenant service that stores US government data in a segregated community cloud.

Microsoft provided the update on Azure Government Cloud during the Microsoft Federal Virtual Forum event.