By appointing Brennan to the post, Obama has got an influential adviser on the Middle East and Iran.
Incidentally, Brennan had called for a sharp break with the past US policy regarding the Middle-East, and Iran.
The appointment comes six weeks after he (Brennan) was forced to pull out of contention for the directorship of the Central Intelligence Agency (CIA), because of fears that his statements supporting some controversial interrogation techniques would have complicated his confirmation to the post, the Washington Post reported.
Brennan was in the news recently for defending the CIA's long-standing practice of forced renditions, or transfers, of terrorism suspects for interrogations, a position that forced his withdrawal of his candidacy to head the CIA.
He also had to face personal criticism from human rights experts regarding his view on the trial and transfer of terror suspects.
Brennan a CIA veteran, currently heads a private counterterrorism firm, the Analysis Corporation. The firm has been providing services to several federal agencies and private firms on counterterrorism over the last one decade.