White House approves broader Yemen drone campaign The United States has begun launching drone strikes against suspected al-Qaeda operatives in Yemen under new authority approved by President Obama that allows the CIA and the military to fire even when the identity of those who could be killed is not known, U.S. officials said. The policy shift marks a significant expansion of the clandestine drone war against an al-Qaeda affiliate that has seized large ­pieces of territory in Yemen and is linked to a series of terrorist plots against the United States. U.S. officials said that Obama approved the use of "signature" strikes this month and that the killing of an al-Qaeda operative near the border of Yemen's Marib province this week was among the first attacks carried out under the new authority. The decision to give the CIA and the U.S. Joint Special Operations Command (JSOC) greater leeway is almost certain to escalate a drone campaign that has accelerated significantly this year, with at least nine strikes in under four months. The number is about equal to the sum of airstrikes all last year. The expanded authority will allow the CIA and JSOC to fire on targets based solely on their intelligence "signatures" - patterns of behavior that are detected through signals intercepts, human sources and aerial surveillance, and that indicate the presence of an important operative or a plot against U.S. interests. Until now, the administration had allowed strikes only against known terrorist leaders who appear on secret CIA and JSOC target lists and whose location can be confirmed. Moving beyond those rules of engagement raises substantial risks for the Obama administration, which has sought to avoid being drawn into a fight between insurgents and Yemen's central government. Congressional officials have expressed concern that using signature strikes would raise the likelihood of killing militants who are not involved in plots against the United States, angering Yemeni tribes and potentially creating a new crop of al-Qaeda recruits. Critics have also challenged the legal grounds for expanding the drone campaign in Yemen. In an opinion piece published in The Washington Post on Sunday, Bruce Ackerman, a law professor at Yale University, argued that war measures adopted in the aftermath of the Sept. 11, 2001, attacks were not aimed at al-Qaeda's Yemeni affiliate and don't provide Obama "with authority to respond to these threats without seeking further congressional consent." The Post reported last week that the CIA was seeking authority to expand the drone campaign in Yemen. The approval of that enhanced authority was first reported Wednesday on the Wall Street Journal's Web site. CIA and White House officials declined to comment. Administration officials stressed that U.S. airstrikes in Yemen will still be under tighter restrictions than they have been in Pakistan. CIA drones flying over Pakistan's tribal belt are allowed to strike groups of armed militants traveling by truck toward the war in Afghanistan, for example, even when there is no indication of the presence of al-Qaeda operatives or a high-value terrorist.