WASHINGTON: The CIA received approval to target a wider range of targets in Pakistan's tribal areas, including low-level fighters whose identities may not be known, US officials said on Wednesday.
The expanded strikes began under President George W Bush and have accelerated under President Barack Obama.
Supporters credit the covert targeted killing program with dealing a serious blow to al Qaeda and the Taliban, benefiting US forces in neighbouring Pakistan.
Critics say the expanded CIA strikes raise legal as well as security concerns amid signs the suspect behind Saturday's attempted car bombing in New York's Times Square had ties to the Pakistani Taliban movement, known as Tehrik-e-Taliban Pakistan, or TTP.
Despite initial US skepticism, an official said TTP links to the case looked increasingly "plausible."
CIA-operated drones have aggressively targeted TTP leaders over the past year in Pakistan's tribal areas, and the group has vowed to avenge strikes that have killed several top leaders and commanders.
Current and former officials said government lawyers backed expansion of the "target set" for CIA drone strikes on self-defense grounds based on the threat the fighters pose to US forces in Afghanistan and the United States as a whole.
In his few public references to the drones, Obama cited what he called the need to "take out high-level terrorist targets" if Pakistan would not.
"Targets are chosen with extreme care, factoring in concepts like necessity, proportionality, and an absolute obligation to minimize loss of innocent life and property damage," a US counterterrorism official said.
Of the 500 suspected militants whom the United States believes the drones have killed since the summer of 2008, only 14 are widely considered to be top-tier militant targets, while 25 others are considered mid-to-high-level organizers.
Former intelligence officials acknowledged that in many, if not most cases, the CIA had little information about the foot soldiers killed in the strikes.
The counterterrorism official denied that strikes against fighters were "random."
"Counterterrorism operations are driven by information and observation, gathered over time. You can track individuals, and -- patiently and carefully -- build up a picture of how they move, where they go, and what they see. That makes it easier to determine when and how to take action," the official said.
Jeffrey Addicott, director of the Center for Terrorism Law at St. Mary's University, said the CIA's goal in targeting foot soldiers was to "demoralize the rank and file."