The White House legal counsel, Gregory Craig, intends to announce his resignation on Friday, according to US media outlets.
The New York Times reported that questions have circulated inside the White House about his status for months, but an official said early Friday that Craig had made the decision to resign.
Craig had been at the center of controversial decisions over whether to close the Guantanamo Bay prison as well as revising administration policies on the interrogation and detention of prisoners.
The notorious military detention center has been widely criticized around the world for its harsh interrogations.
President Obama ordered the prison closed when he took office but administration officials have run into numerous legal, political and diplomatic hurdles.
Craig would be replaced by Bob Bauer, a Democratic lawyer in Washington, who has represented Obama for years, the Times said.