After a nearly 13-hour filibuster led by Sen. Rand Paul over drone strike policies within U.S. borders, senators took procedural steps early Thursday to advance the nomination of John O. Brennan to be CIA director.

At 12:40 a.m., the Kentucky Republican finally yielded the floor after a long day in which he and other GOP senators argued the White House should rule out the use of drone strikes on American soil.

“I just hope this won’t be swept under the rug,” Paul said. “I would go another 12 hours, but I’ve discovered there are some limits to filibustering, and I have to take care of one those in just a few minutes here.”

With Paul finally out of steam, a group of six senators who aided Paul’s filibuster with numerous and lengthy questions watched as Majority Whip Richard J. Durbin, D-Ill., came to the floor and filed a cloture motion to cut off debate on Brennan’s nomination.

Under Senate rules, the motion would require an intervening day before the Senate could vote to limit debate on the Brennan nomination. That would set up a Saturday vote one hour after the Senate reconvenes, absent the consent of all senators to move the vote up. If senators agree to cloture, which would require 60 votes, there would be eight hours of post-cloture debate before a final vote on the nomination unless senators decide to yield back the time.

Majority Leader Harry Reid, D-Nev., tried Wednesday afternoon to get an agreement to hold a cloture vote in the evening, but Paul said he would not consent until the White House answered his questions on the legality of drone strikes in the United States. Later Wednesday evening, Paul tried to set up a vote on a resolution that would express the sentiment that military drone strikes on U.S. soil violate due-process rights of Americans in exchange for a vote on Brennan. But this time it was Durbin who objected.

Although Paul may not get an answer to his questions, he has brought attention to the issue of drones and lethal force, a policy area that Brennan has had a hand in as the top White House counterterrorism and homeland security adviser. Paul’s filibuster has renewed opposition to Brennan’s nomination.

As the clock approached midnight, fellow Kentucky Republican Mitch McConnell, the minority leader, came to the floor in support of Paul’s filibuster.

“At whatever point we get to a cloture vote to extend debate on the nomination of Brennan, it is my view that cloture should not be invoked,” McConnell said. “This is a controversial nominee.”

When the Senate started legislative business Wednesday morning, Reid said he was willing to impose a 60-vote threshold on Brennan’s confirmation vote to avoid a filibuster of the nomination.

“If someone doesn’t like him, come here and give a big speech, wave your arms, scream and shout and vote against him,” Reid said. “But why hold up the entire Senate over a meaningless vote?”

As a winter storm beset the capital region, Paul took Reid up on the first half of his offer.

“I will speak until I can no longer speak,” Paul said. “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 to be guilty by a court.”

Paul said letters sent to him from Attorney General Eric H. Holder Jr. and Brennan had not addressed his question on whether the government could conduct drone strikes on U.S. soil. Although Brennan told him in a letter March 5 that the CIA neither conducts, nor has authority to undertake, lethal attacks within the United States, Holder wrote March 4 that there might be extraordinary circumstances, such as the 2001 terrorist attacks or Pearl Harbor, where the government might have that authority. Paul referenced the responses on the Senate floor.

“You see, the drone strike program is under the Department of Defense,” Paul said, “so when the CIA says they’re not going to kill you in America, they’re not saying the Defense Department won’t.”

Over and over, Paul repeated his demand for assurances from President Barack Obama that his administration would not order strikes against Americans, even saying late Wednesday night that he would settle for a tweet.

The White House has not responded to Paul’s request.

Benghazi, ‘Enhanced’ Interrogations

Although Paul was the main attraction in the Senate on Wednesday, he is not the only senator seeking information from the White House.

Republicans John McCain, of Arizona, and Lindsey Graham, of South Carolina, also may challenge Brennan’s nomination over questions related to the Benghazi attack. On Tuesday, McCain repeated his concerns about Brennan’s role in the CIA’s enhanced interrogation program.

“I want to know what his position is,” McCain said. “On one hand he said he condemned them, on the other hand he said it saved lives. I don’t know how you reconcile those two positions.”

Brennan withdrew from consideration to be CIA director four years ago over questions surrounding his role in the use of enhanced interrogation techniques under President George W. Bush. During his Intelligence Committee hearing Feb. 7, Brennan denied playing a central role in the CIA program, which included the use of such controversial methods as waterboarding.

Legal Opinions on Drone Strikes

Some senators who had threatened to block Brennan’s nomination softened their stances on Tuesday.

Before the Senate Intelligence Committee approved Brennan’s nomination Tuesday, Chairwoman Dianne Feinstein, D-Calif., said the administration would supply the panel with requested legal opinions on the targeted killing of U.S. citizens suspected of terrorism overseas.

That decision earned Brennan the support of Ron Wyden, D-Ore., who was considering a hold on the nomination, as well as Mark Udall, D-Colo., and Susan Collins, R-Maine.

Scott Campbell contributed to this story.