Washington (CNN) – Sen. Rand Paul, one of the most outspoken critics of President Barack Obama's use of drones to target terrorists overseas, vowed Wednesday to hold up the nomination of one of the program's chief architects.
John Brennan, Obama's top counterterrorism adviser, is under consideration by the Senate to become the next director of the Central Intelligence Agency. The president nominated him to the post last month.
In a statement, Paul - a Republican from Kentucky - wrote that he still has questions for Brennan surrounding the drone program.
"I have asked Mr. Brennan if he believed that the President has the power to authorize lethal force, such as a drone strike, against a U.S. citizen on U.S. soil, and my question remains unanswered," Paul wrote. "I will not allow a vote on this nomination until Mr. Brennan openly responds to the questions and concerns my colleagues and I share."
Paul, along with some fellow Republicans and Democrats, have called into question the legality of targeting Americans abroad who are suspected of being terrorists. Such a situation arose in 2011, when an American drone was used to kill New Mexico-born Anwar al-Awlaki - who officials said played an operational role in al Qaeda in the Arabian Peninsula.
On Sunday, Paul said on CNN's "State of the Union" the current system vested too much power in the president, and that measures were needed to ensure that power doesn't go unchecked.
"It's very unseemly that a politician gets to decide the death of an American citizen," Paul said. "There needs to be a trial for treason. The president, or a politician, Republican or Democrat, should never get to decide someone's death by flipping through flash cards."
Paul, who is considered a potential candidate for the 2016 GOP presidential nomination, delivered the tea party response to Tuesday night's State of the Union address. He used similar language during those remarks to denounce the use of drones to kill Americans.