US officials have agreed to release to Congress documents justifying drone strikes on Americans suspected of working with terrorist groups.
The justice department acted after NBC News published a leaked internal memo outlining some of the legal arguments.
President Barack Obama’s choice for CIA director, John Brennan, is likely to face questions on the programme during a Senate confirmation hearing later.
He is believed to have overseen the drone programme, escalated by Mr Obama.
On Wednesday it was revealed that the Central Intelligence Agency had been operating a secret drone base in Saudi Arabia for the past two years.