The approval will allow RIM's single largest customer to upgrade to the Canadian smartphone maker's latest phones as it waits for the launch of its next-generation BlackBerry 10 devices later this year.

U.S. Army and other Defense Department personnel have long used BlackBerry phones, but each new version of the device requires testing before authorities can approve its use in sensitive roles where a data breach could endanger national security.

The department - which manages U.S. military forces - had previously relied on BlackBerry devices using earlier versions of the operating system, which are bogged down by a relatively slow Internet browser and other shortcomings.

The department is also working to introduce a mobile device using a hardened version of Google Inc's Android software. RIM has said around 250,000 BlackBerry smartphones are used in the department, which is the world's largest employer.

Barack Obama, who as president serves as commander-in-chief of the U.S. armed forces, uses a modified version of the smartphone.

The U.S. Army last year introduced new applications and capabilities for its BlackBerry users, RIM said. Its personnel can now take advantage of recent advances such as n ear field communications, augmented reality and voice-activated universal search.

RIM's Scott Totzke said security was crucial for some government and corporate customers. But, he added, "leveraging the full power of BlackBerry smartphones is also important as it helps them realize the full potential of their investment in the BlackBerry platform."

RIM's shares, which have fallen 74 percent in the last year and wallow at eight-year lows, were 0.3 percent lower at $11.97 on the Nasdaq by mid-afternoon.

(Reporting by Alastair Sharp in Toronto and Abhiram Nandakumar in Bangalore; Editing by Frank Mcgurty)

• A Permanent Economic Emergency