Obama to bring US drone programme out from 'legal shadows' of the CIA US military likely to now work within a new set of legal guidelines agreed by Obama this week. The White House was due to announce a series of measures aimed at moving the controversial US drone killings programme out of the "legal shadows" on Thursday. In a major counter-terrorism speech billed as marking the end of an unfettered "war" on terror, Barack Obama was expected to reveal that he will move responsibility for future drone operations from the CIA to the Pentagon so they can be more closely monitored by Congress. A more limited range of strikes in countries such as Yemen are likely to be carried out by the US military working within a new set of legal guidelines agreed by Obama this week, giving greater clarification on how and when officials can target suspected terrorists operating abroad. Attorney general Eric Holder told congressional leaders in a letter on Wednesday that they would be briefed in private on whether future drone attacks on suspected terrorists passed the new legal threshold. Both the White House and the CIA declined to comment on details of the policy ahead of the speech but government sources told the Guardian they would add to existing congressional oversight measures in place. Until recently the administration did not even publicly admit the existence of the drone programme. Human rights campaigners have cautiously welcomed the attempt to bring US drone warfare policy into the open, but called on President Obama to publish the new legal tests that he was due to announce later on Thursday. Dixon Osburn, a director at Human Rights First, said: "On its own, it is not clear that taking things away from the CIA makes a difference - the special operations command at the Pentagon is also secret - but at least the military are schooled in the rules of war." Earlier, the White House marked this new effort to draw a line under the controversial drone-strike policy by admitting for the first time that four American citizens were among those killed by its covert attacks in Yemen and Pakistan since 2009. In a letter to congressional leaders sent on Wednesday, attorney general Eric Holder Holder claimed one of the US citizens killed, Anwar al-Awlaki, was chief of external operations for al-Qaida in the Arabian Peninsula (Aqap) and had been involved in plots to blow up aircraft over US soil. "The president will soon be speaking publicly in greater detail about our counter-terrorism operations and the legal and policy framework," Holder told 22 senior members of Congress in Wednesday's letter. White House spokesman Jay Carney said Obama would also outline his renewed attempt to shut the Guantánamo Bay detention centre in the speech, and seek to explain why previous efforts had failed. The White House said Thursday's speech will cover "broad counter-terrorism policy, including military, diplomatic, intelligence, and legal efforts." And he will frame the future of our efforts against al-Qaida, its affiliates and its adherents.