By Tabassum Zakaria and Mark Hosenball
WASHINGTON, May 23 (Reuters) - New U.S. guidelines for conducting armed drone operations overseas set a higher bar for attacking non-Americans and could reduce controversial "signature strikes" targeted at suspicious groups rather than individuals.
But the drone guidelines announced by President Barack Obama on Thursday still include vague language and loopholes that officials could use to conduct more expansive operations.
The new rules, part of Obama's attempts to pull back from what he called "perpetual war-footing" against terrorism, came in a "Presidential Policy Guidance" he signed this week.
Obama "has clearly raised the bar significantly for the use of drone strikes with the very specific and restrictive criteria," said John Bellinger, former State Department legal adviser in President George W. Bush's administration.
"The standard for targeting is now the same for Americans and non-Americans - it must be a continuing and imminent threat of violence to Americans. And there must be a near certainty that no non-combatants will be killed," he said.
"Signature" drone strikes, in which the United States targets suspicious-looking groups of people without knowing their specific identities were first authorized by Bush in 2008, causing a sharp jump in the number of drone attacks.
During his first term in office, Obama stepped up the practice. People not confirmed as terrorist targets of the United States are attacked because they bear the "signature" of militant activity. Such strikes have provoked anti-American unrest in countries like Pakistan because of civilian deaths.
Under Obama's new guidelines, signature attacks are expected to decline, especially after U.S. forces withdraw from Afghanistan in 2014, when the need for drone strikes to protect U.S. ground forces will be gone.
The reason for signature strikes is often to help a country like Yemen fight well-organized groups of militants, and targets are frequently brought to the attention of the United States by the Yemeni government, said Kenneth Anderson, a law professor at American University.
"That's the biggest thing that it appears that they have given up, that we won't be striking on behalf of allies fighting their own wars," he said.
The New America Foundation think tank, which collects data on drone strikes, said 355 drone attacks in Pakistan had killed between 2,010 and 3,336 people, among whom 258 to 307 were civilians. In Yemen, 69 drone strikes have killed between 586 and 819 people, of whom 548 to 748 were militants.
Faced with criticism about civilian casualties, Obama said the United States would only use those drone strikes when a threat was "continuing and imminent," a nuanced change from the previous policy of launching strikes against a significant threat.
Paul Pillar, a former CIA analyst, said that was too vague.
"It still leaves questions and doubts. One piece of phraseology that should raise questions is the somewhat oxymoronic 'continuing, imminent threat.' If a threat is continuing, how can it be imminent, except maybe at one particular time before it is finally executed? " he said.
The new Obama drone policy also states a preference for having future strikes conducted by the military. Until now, the CIA had been the main agency conducting drone strikes outside war zones in places like Pakistan.
The administration made public few details about how the shift in control of drone operations would be carried out. But government sources told Reuters earlier this week that shifting operations to the Pentagon would be done in stages and that the CIA would keep conducting strikes in Pakistan for the time being.
One government source said that for the moment, the decision as to which agency conducts a drone attack would likely be determined on a case-by-case basis rather than a hard rule based on geography.
Another government source said the process outlined by Obama would involve a "lot more people" in deciding who gets killed, where, when and how, leading to a cumbersome and time-consuming process. (Reporting by Tabassum Zakaria and Mark Hosenball; Editing by Peter Cooney)