Kentucky senator speaks in protest at comments from officials over possibility of carrying out drone strikes on US soil

Senator Rand Paul on Wednesday began a rare talking filibuster in order to try and block the appointment of John Brennan as CIA chief over his attitude to President Barack Obama's controversial drones policy.

The move, made famous in popular culture by James Stewart in the film Mr Smith Goes to Washington, involves trying to block a piece of legislation by speaking for as long as possible, though rule changes have largely reduced it to a publicity stunt.

In an unexpected development, Paul was joined by Democratic senator Ron Wyden, from Oregon, who warmly praised the Kentucky Senator's move and gave the anti-drones protest a sudden flush of cross-party support. Like Paul, Wyden has been a longstanding critic of aspects of Obama's use of drones. Five Republicans also joined in by making statements.

Paul, a Kentucky senator and son of libertarian hero and former presidential hopeful Ron Paul, said he was making the filibuster attempt out of outrage at recent comments made by Obama officials on the possible legality of carrying out drone strikes against US citizens on American soil.

Rand's filibuster pushed into Thursday and ended more than 12 hours after he began speaking. He had started just before noon on Wednesday; he finally finished speaking and ceded the floor at about 12.40am local time.

In a show of support the Republican Senate minority leader, Mitch McConnell, came to the floor and congratulated Paul for his "tenacity and for his conviction". McConnell also called Brennan a "controversial nominee."

Brennan is an advocate of Obama's greatly expanded drones programme, which has been used to strike suspected Islamist militants abroad. Defenders say it is an effective way of hitting terrorists, while critics say it causes too many civilian casualties, hurts America's image and has been used illegally to kill several US citizens.

"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.

Paul's protest came after comments by Eric Holder on the legality of using drones domestically. Paul made public two letters written to him by Holder, in which the attorney general admitted that it was hypothetically possible for such a scenario to emerge.

"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 authorise the military to use lethal force within the territory of the United States," Holder wrote, though he stressed such a possibility was "unlikely".

Paul's speech began on the Senate floor at just after 11.45am ET on Wednesday. After about an hour he admitted his throat was getting dry and said: "I can't talk forever." But after more than two hours he was still going strong, striking the themes of citizens' constitutional rights over government power that have made him a Tea Party favourite and hero of libertarian-leaning followers of his father. "The constitution limits power given to Congress. But it does not limit rights," he said.

And more than four hours after beginning Paul was joined by the Democrat Wyden. Though Wyden said he was still supporting Brennan's appointment, he raised many of the same questions as Paul. "Every American has the right to know when their government can kill them," he said. He added: "More needs to be done … What are the limitations with respect to this lethal authorities, in particular whether they can be used inside the United States?"

The last talking filibuster in the Senate was in 2010 and carried out by independent socialist senator Bernie Sanders of Vermont. He spoke against extending the Bush tax cuts for the wealthy and lasted eight hours and 37 minutes.

Though Paul began his speech as a lone figure in a virtually empty chamber he was eventually joined by fellow Republican senators Marco Rubio of Florida, Ted Cruz of Texas, Mike Lee of Utah, Saxby Chambliss of Georgia and Jerry Moran of Kansas.

Cruz, whom like Paul is a Tea Party favorite, had also grilled Holder at a Senate committee on Wednesday on the terms by which a US citizen could be killed on American soil. Holder defended his letter to Paul saying that he believed such an action would be considered possible only to prevent attacks like Pearl Harbor or 9/11. Cruz said he would be introducing legislation to outlaw the possibility of killing US citizens absent any imminent threat.

Cruz read Twitter messages from people eager to "Stand With Rand". And as the night went on Cruz spoke for longer periods as Paul leaned against a desk across the floor. Cruz, an insurgent Republican with strong backing from the conservative tea party movement, read passages from Shakespeare's Henry V and lines from the 1970 movie Patton starring George C Scott.

The lethal use of drones to kill targets, especially against US citizens abroad such as the militant Islamist cleric Anwar al-Awlaki and his 16-year-old son, has prompted outrage across the American political spectrum. Numerous conservatives, liberals and civil rights groups have complained that the Obama administration's drones programme is too frequently used, cloaked in legal secrecy and not given enough oversight outside the White House.

In the face of such criticism, the Obama administration has been forced into agreeing to provide access to select members of Congress to its legal justification for targeting and killing American citizens abroad. Obama last month ordered the Justice Department to privately lay out its legal arguments to congressional intelligence committees in a move that ended a two-year battle over attempts the sensitive memos secret.

Paul's stunt to block Brennan is unlikely to amount to any practical obstacle to his appointment. The Senate intelligence committee has already voted in favor of his nomination by 12 votes to three.