Profile: John Brennan
John Brennan, a member of President Barack Obama's inner circle and his top counter-terrorism adviser, is to be officially nominated to direct the Central Intelligence Agency.
During his time with the Obama administration, the 57-year-old played a critical role in the planning of a May 2011 raid that killed Osama Bin Laden.
He has also led the administration's efforts to curb the growth of terror groups in North Africa and the Middle East.
Pending Senate confirmation, he would succeed retired General David Petraeus, who resigned in November after admitting to an extramarital affair with his biographer.Drones in spotlight
Mr Brennan, 57, is a veteran of the CIA, having spent 25 years at the agency in various posts including station chief in Saudi Arabia and deputy executive director in the administration of former President George W Bush.
But some liberals have raised concerns over his involvement in what the government has called "enhanced interrogation techniques" - considered by some to amount to torture.
In 2008, Mr Brennan was reportedly considered for the top job at the CIA, but he withdrew his name amid criticism, while denying any connection to the interrogation methods.
At the time, Mr Brennan said in a letter to Mr Obama that he had been "a strong opponent of many of the policies of the Bush administration, such as the pre-emptive war in Iraq and coercive interrogation tactics, to include waterboarding".
Many analysts say it is unlikely that he will face such criticism this time round.
But, they say, Mr Brennan's nomination is likely to bring renewed focus to the government's drone policy.
In April, Mr Brennan became the first member of Mr Obama's administration to make detailed public comments acknowledging the government's use of unmanned drones to carry out targeted killings.
Speaking to a think tank in Washington, Mr Brennan argued that the overseas attacks were legal, and protected the lives of Americans.
Ahead of its announcement, the White House has said that, over the last four years, Mr Brennan has worked closely with the president and has been involved with "virtually all major national security issues and will be able to hit the ground running at the CIA", according to Politico.