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 U.S. 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 U.S. scepticism, 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-defence grounds based on the threat the fighters pose to U.S. 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.
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, U.S. officials said on Wednesday.
First Published: Thursday, May 06, 2010, 11:53