President Barack Obama has nominated a US Navy officer, Vice Admiral Michael Rogers, to take over as head of the National Security Agency (NSA) that has recently come under fire over its practises.

"This is a critical time for the NSA, and Vice Admiral Rogers would bring extraordinary and unique qualifications to this position as the agency continues its vital mission and implements President Obama's reforms," Defence Secretary Chuck Hagel, who recommended Rogers for the post, said in a statement on Thursday.

Rogers would also take over as head of the military's Cyber Warfare Command.

Rogers, 53, would take the helm at a difficult moment for the spy agency, which has been rocked by former analyst Edward Snowden's disclosures of its secret surveillance programmes that collect phone and internet data around the world and now faces enormous pressure to change its ways.

Spy agency reforms

In response to the furore triggered by the leaks, Obama proposed reforms to rein in the NSA's spying authority in some areas.

Hagel said he was "confident that Admiral Rogers has the wisdom to help balance the demands of security, privacy and liberty in our digital age".

Rogers, who trained as an intelligence cryptologist and is a former intelligence director for the Joint Chiefs of Staff, would succeed General Keith Alexander, who has served in the top job since 2005, and plans to retire mid-March.

He currently heads the US Fleet Cyber Command, overseeing the navy's cyber warfare specialists.

In more than 30 years in the Navy, Rogers has worked in cryptology, eavesdropping or "signals intelligence" and cyber warfare.

Like Alexander, the naval officer would not only run the powerful NSA but would also serve as chief of the US military's Cyber Command.

Obama has decided to keep the "dual-hatted" arrangement, even though some top officials recommended splitting up the two jobs.

The president has rejected suggestions to name a civilian as NSA director.

Source: Agencies