WASHINGTON -- In the wake of Sen. Rand Paul's 13-hour filibuster, Senate Majority Leader Harry Reid said the Senate would vote on Saturday to end debate on President Obama's nominee to head the CIA, unless lawmakers reach an agreement to vote earlier.

Paul, who started speaking about 11:45 a.m. Wednesday, ended his filibuster shortly after midnight Thursday. His comments were less about John Brennan, Obama's CIA nominee and counterterrorism adviser, and more about the constitutionality of drone strikes on U.S. citizens at home and abroad without due process.

While Paul, R-Ky., ended his filibuster, Senate Majority Leader Mitch McConnell, also a Kentucky Republican, said he would continue to oppose Brennan's nomination and attempts to end debate on it.

"I'm going to speak as long as I can to draw attention to something I find very disturbing," Paul said when he started speaking Wednesday.

Senate Judiciary Chairman Pat Leahy, D-Vt., announced at a gun hearing Wednesday that the committee was planning a March 20 hearing to examine the domestic use of drones.

What started as a solo effort turned into a multi-senator debate that included one Democrat, Ron Wyden of Oregon, and at least seven Republicans questioning the constitutionality of drone strikes on U.S. citizens at home and abroad.

In a show of support, several of Paul's colleagues who share his conservative views came to the floor to take turns speaking for him and trading questions. Sen. Ted Cruz, R-Texas, read Twitter messages from people eager to "Stand With Rand." Sen. Marco Rubio, R-Fla., made references to rappers Jay-Z and Wiz Khalifa.

"No American should be killed by a drone on American soil without first being charged with a crime, without first being found guilty of a crime by a court," Paul said. "How can you kill someone without going to a judge, or a jury?"

Paul, a critic of Obama's unmanned drone policy, started his filibuster by demanding the president or Attorney General Eric Holder issue a statement assuring that unmanned aircraft would not be used in the United States to kill terrorism suspects who are U.S. citizens.

Paul said his focus was on constitutional issues. "We really just want (Obama) to say he won't" attack non-combatants on U.S. soil.

While Paul said he cared more about the constitutionality of drone strikes, some of his fellow Republicans jumped on the filibuster as a way to raise money. The National Republican Senatorial Committee sent alerts Wednesday soliciting donations and mentioned Paul. Sen. Jerry Moran, R-Kan., who chairs the NRSC participated in the filibuster with Paul.

The federal government has not conducted such operations and doesn't plan to, Holder told Paul in a March 4 letter. But, Holder added, it was possible Obama could be forced by an "extraordinary circumstance" to kill citizens inside the United States, and he cited the Pearl Harbor and 9/11 attacks as examples.

During his filibuster, Paul said the fuzziness of such language created a slippery slope that could lead to the targeting of citizens who merely have different opinions about policies than the president.

"You can't be judge, jury and executioner all in one," Paul said.

Wyden, a longtime critic of excessive government intelligence and surveillance programs, said "the senator from Kentucky has made a number of important points."

There are times, Wyden said, when a U.S. citizen who takes up arms against the United States while overseas can be attacked by a drone. But the executive branch of government, he said, should not be allowed to "conduct such a far-reaching policy without scrutiny."

It's not a partisan issue, Paul said, noting that he voted to support the nominations of John Kerry and Chuck Hagel, the secretaries of State and Defense.

Paul and other senators had delayed a full Senate vote on Brennan's nomination until they received more information about the drone program. The White House provided Justice Department documents on the drone program to the Senate Intelligence Committee on Tuesday.

The committee then voted 12-3 to approve Brennan's nomination.

While Paul's filibuster gathered favorable attention throughout the day and into the night Wednesday, not all conservatives were impressed. The conservative editorial page of The Wall Street Journal said: "The country needs more Senators who care about liberty, but if Mr. Paul wants to be taken seriously he needs to do more than pull political stunts that fire up impressionable libertarian kids in their college dorms. He needs to know what he's talking about."

Sen. John McCain, R-Ariz., also criticized the filibuster on the Senate floor Thursday, saying the participants "should know better."

Brennan has been closely linked to the drone program. The administration has used the unmanned aircraft to regularly target suspected terrorists in the Middle East and Africa.

In 2011, U.S.-born cleric Anwar al-Awlaki was killed by a drone strike in Yemen, raising questions about the use of the armed drones on American citizens.

Before coming to the White House, Brennan served 25 years in the CIA.

Contributing: Susan Davis in Washington; Alia E. Dastagir in McLean, Va.; the Associated Press