President Barack Obama is due to announce a major shift in US unmanned drone strike policy, with plans to restrict their scope and expand their transparency in a major speech on counter-terrorism today.
It will be the first time Obama has discussed the controversial policy in a public speech, and comes a day after the US government confirmed for the first time that four US citizens had been killed in the strikes.
"He will discuss why the use of drone strikes is necessary, legal and just, while addressing the various issues raised by our use of targeted action," a White House official told the New York Times.
The lethal strikes will only be used against targets who pose "a continuing, imminent threat to Americans" and cannot feasibly be captured, Attorney General Eric H. Holder Jr. said in a letter to Congress, suggesting that threats to countries such as Pakistan or Yemen would not be sufficient to justify a strike.
Previously, the strikes have been criticised for targeting groups for being suspected of belonging to Al-Qaida or affiliated groups, and causing civilian deaths.
The restriction in focus is seen as bringing the policy in line with peacetime protocol, rather than war zone protocol.
Obama will also announce plans to close the Guatanamo Bay detention camp and step up efforts to repatriate its inmates. In the past he has called the camp "harmful to who we are" and detrimental to US interests.
Responsibility for the programme is also due to be handed from the CIA to the Pentagon, allowing the US House of Congress some powers of oversight over their use.
White House spokesman Jay Carney said on Wednesday that Mr Obama "believes that we need to be as transparent about a matter like this as we can.
"It is his belief that there need to be structures in place that remain in place for successive administrations... [so that counter-terrorism policy is] conducted in a way that ensures that we're keeping with our traditions and our laws".
Dixon Osburn of Human Rights First welcomed the shift, but said in a statement he remained "deeply concerned that the administration appears to be institutionalising a problematic targeted killing policy without public debate".
In his letter, Holder confirmed the identities of the four US citizens killed in drone strikes.
He defended the killing of Anwar Al-Awlaki in an attack in 2011, describing the victim, who was born in New Mexico, as a "senior operational leader" of Al-Qaeda. Naturalised US citizen Samir Khan, who ran an online magazine devoted to Islamist ideology which was reportedly read by Boston bomber Tamerlan Tsarnaev, was killed in the same strike.
Al-Awlaki's 16-year-old US-born son Abdulrahman was killed in a drone strike in Yemen the following month.
He also confirmed that Jude Kenan Mohammed, of North Carolina, who was suspected of being part of a terrorist conspiracy, was killed in a strike in Pakistan in 2011.