The US House of Representatives on Wednesday continued for a second day its historic inability to approve a speaker as Republican Kevin McCarthy failed to get the needed votes on three more ballots, blocked by hard-line conservatives who ignored a plea from former president Donald Trump to unite behind the California congressman.

After a sixth ballot, the House on Wednesday had adjourned until 8 pm but still couldn't reach a breakthrough. The chamber then barely voted to adjourn until noon on Thursday, with Democrats opposed.

"I don't think voting tonight is productive," McCarthy said after the late vote to adjourn until Thursday. But he said voting "in the future will make a difference".

The failure to elect a new speaker is delaying the swearing in of hundreds of members of Congress, putting off any legislative work.

Trump said McCarthy "will do a good job, and maybe even a GREAT JOB" but he failed to sway 20 Republicans — the same number who voted against McCarthy in the final of three ballots Tuesday.

Just hours before voting began Wednesday, former vice-president Mike Pence joined Trump and urged Republicans to rally around McCarthy.

But Colorado Representative Lauren Boebert finished her renomination speech for Florida Representative-elect Byron Donalds in the fifth ballot by saying Trump should tell McCarthy, "Sir, you do not have the votes, and it's time to withdraw.

Florida Representative Matt Gaetz, one of Trump's staunchest congressional supporters and one of the 20 House Republicans opposing McCarthy's bid, dismissed Trump's effort, calling it "sad".

Later on Wednesday, Trump wrote on his social media platform that he "always supported" Donalds and "consistently endorsed him''. The 44-year-old is "a young man with a great future!" Trump wrote. "He will have his day, and it will be a big one, but not now!"

Trump also wrote that a statement circulating publicly claiming that he had endorsed Donalds for speaker is "fake and fraudulent".

Gaetz on Wednesday demanded to know why McCarthy was using the office reserved for the House speaker after losing three straight votes on Tuesday. Gaetz suggested McCarthy could eventually be physically removed from the office if he doesn't win the speaker's race soon.

"How long will he remain there until he is considered a squatter?" Gaetz said.

McCarthy was considered the presumptive speaker of the House since winning a majority of his Republican colleagues in a caucus vote after the midterm election.

More than half of the lawmakers who have voted against McCarthy have said that the 2020 election had been stolen or rigged or that Trump was the rightful winner over Joe Biden, according to The New York Times.

The dissenters who voted for Ohio Representative Jim Jordan in the third vote yesterday all backed Donalds as a new alternative, knowing he won't win but showing their dissatisfaction with McCarthy.

Donalds has represented a Florida district since 2021 and was one of 147 Republicans who voted to reject the results of the 2020 presidential election.

In nominating him at the start of the fourth vote on Wednesday, Representative Chip Roy of Texas noted that Donalds is black and that this was the first time two black candidates had been nominated for speaker.

The Democratic nominee, Representative Hakeem Jeffries of New York, became the first black leader of any party's House caucus on Tuesday. There has never been a black speaker.

Donalds said on Twitter this week that McCarthy "doesn't have the votes" to win.

After losing on the first three ballots Tuesday, McCarthy switched strategies Wednesday by asking Republican members who oppose him to vote "present" rather than backing another candidate, a move to lower the threshold needed to win the speakership.

Only one lawmaker who had voted for McCarthy three times voted present.

Instead, the 20 GOP lawmakers remained steadfast Wednesday by throwing their support to Donalds, and McCarthy lost three more votes Wednesday afternoon.

The thin Republican majority in the House means almost all the party's members must agree on a speaker. If all members of the House are voting and participating, the winner needs 218 votes. Republicans control 222 seats. On Tuesday, McCarthy drew at most 203 votes. On Wednesday, his total slipped to 201.

"Well, it's Groundhog Day," said Florida Representative Kat Cammack in nominating McCarthy on the sixth ballot.

She said, "To all Americans watching right now, we hear you. And we will get through this — no matter how messy."

Biden on Wednesday called the chaos in the House an embarrassment to the United States on a global stage.

"It's a little embarrassing that it's taking so long and the way they're dealing with each other — and the rest of the world is looking," he told reporters at the White House.