Deputy National Security Adviser John Brennan
Deputy National Security Adviser John BrennanReuters

Senator Rand Paul (R-KY), irate over the Obama administration's refusal to rule out drone strikes on American soil, took to the Senate floor Wednesday in a classic filibuster to block the president's nominee to lead the Central Intelligence Agency (CIA).

The issue gained momentum on Capitol Hill with senators from both parties pressing US Attorney General Eric Holder for more details on whether the administration believes such attacks could be justified.

Paul said he would "speak until I can no longer speak,” demanding answers from President Barack Obama on the secret unmanned aerial drone program that has emerged as the most contentious element of John Brennan's nomination to head the spy agency.

"I will speak as long as it takes until the alarm is sounded from coast to coast that our Constitution is important, that your rights to trial by jury are precious, that no American should be killed by a drone, on American soil, without first being charged with a crime, without first being found guilty by a court," Paul said, according to AFP.

The Senate Democratic leadership said they intended to move this week on a full confirmation vote for Brennan.

His nomination easily cleared the Senate Intelligence Committee Tuesday despite some Republican concerns regarding lack of transparency from the White House on last year's attack in Benghazi, Libya that killed four Americans.

Paul threatened to filibuster Brennan's nomination as early February 13, when he demanded answers from the administration about the president's power to authorize lethal force.

Holder responded Tuesday, stressing that while Obama had "no intention" of ordering drone strikes on US soil, the scenario could be possible if there was an "extraordinary circumstance" such as an attack similar to 9/11.

Paul described the refusal to comprehensively rule out such a strike as "more than frightening," then took to the floor Wednesday to describe the policy as an "abomination."

"When I asked the president, can you kill an American on American soil, it should have been an easy answer.... It should have been a resounding and unequivocal 'no,'" Paul said.

"The president's response? He hasn't killed anyone yet."

"Is that enough? Are we satisfied by that?" Paul asked.

He insisted that his critique was not partisan saying, "Were this a Republican president I'd be here saying exactly the same thing."

Paul began his filibuster at 11:47 am (1637 GMT), and was going strong more than two hours later, recalling the classic "talking filibusters" of old, according to AFP.

The issue became the focal point at a Wednesday hearing where Republican sen. Ted Cruz also confronted Holder about drones.

Cruz asked Holder whether the Constitution would allow a drone strike on an individual sitting at a cafe "if that individual is not posing an imminent and immediate threat of death or bodily harm."

Holder responded by saying, "I would not think that that would be an appropriate use of any kind of lethal force," but declined to answer directly.

The question prompted a fierce response from Cruz, who said it was "remarkable" that the administration could not state unequivocally that such a strike would not be legally allowed.