Attorney General Eric Holder has written a letter to Sen. Rand Paul (R-Ky.) saying that a drone could not be used against a noncombatant American. In response, Paul has said he the Senate should move ahead with John Brennan's nomination as director of the CIA. The vote is being held this afternoon.

The letter followed a 13-hour filibuster of Brennan by Paul and several other senators, who objected to the possibility of domestic drone strikes on U.S. citizens.

"Does the president have the authority to use a weaponized drone to kill an American not engaged in combat on U.S. soil?" Holder's letter reads. "The answer to that is no."

Read: Holder's letter to Sen. Paul

Paul said Thursday afternoon that he's happy with the response and that he urges the Senate to proceed to a vote on Brennan's nomination.

“I’m quite happy with the answer," Paul said. "Through the advise and consent process, I’ve got an important answer."

Paul added of the Brennan vote: "Yes, we’ll hold it as soon as people want to today."

Senate Republicans have said there will be two votes this afternoon, one a 60-vote hurdle to end the filibuster and the other to confirm Brennan as CIA director. Confirmation is expected.

As for his own vote, Paul said: “I’m still thinking about it.” He said there are still questions about the drone program but, "I've kind of won my battle."

In an earlier letter, Holder told Paul that "it is possible, I suppose, to imagine an extraordinary circumstance in which it would be necessary and appropriate under the Constitution and applicable laws of the United States for the President to authorize the military to use lethal force within the territory of the United States."

In a subsequent exchange with Sen. Ted Cruz (R-Texas), Holder said it would not be constitutional to kill a U.S. citizen on American soil if that person does not pose an imminent threat.

White House spokesman Jay Carney told reporters Thursday that "the president has not and would not use drone strikes against American citizens on American soil," suggesting Paul's questions were "wild hypotheticals."