WASHINGTON (AFP) - US President Barack Obama admitted Wednesday he was not allowed to have an iPhone owing to security fears - explaining why he is sometimes seen with a bulky super secure Blackberry.

"I'm not allowed for security reasons to have an iPhone," Mr Obama told a group of young people at the White House for an event promoting his health care law.

He added that his daughters Sasha and Malia spend a lot of time on their iPhones.

Blackberry is renowned for its strong security encryption - one reason why it is still popular in official Washington, even as the device loses market share to other smart phones including those manufactured by Apple.

The security measures on Mr Obama's specially adapted Blackberry came under new scrutiny this year following claims that US spies had eavesdropped on the mobile phone of German Chancellor Angela Merkel.

Within days of being inaugurated president, Mr Obama won his battle with the Secret Service to hang on to his Blackberry, despite fears that it was vulnerable to being hacked, would give away his whereabouts and amid worries that anything he writes could eventually be grist for congressional investigations.

He has been seen scrolling down his messages in his limousine as he travels around.

The president often privately talks of how frustrated he is about the White House "bubble" which makes it very difficult to communicate with normal people or to get information from the outside world that is not filtered for him by aides or the press. Aides say his Blackberry is a way to escape that confinement.

The White House says the president's personal email address was strictly limited to a small list of senior officials and personal friends, but will not detail the encryption devices that are used to secure his communications.