By Susan Heavey and Doina Chiacu

WASHINGTON Embattled U.S. House Speaker Kevin McCarthy said on Tuesday he thought he would survive a leadership challenge from one of his fellow Republicans that could plunge Congress into chaos.

The House of Representatives must act within the next two days on a motion by Representative Matt Gaetz, a far-right Republican and McCarthy antagonist, that could remove McCarthy from his post.

If successful, it would be the first time in U.S. history that House lawmakers voted their leader out. McCarthy suggested a vote could come as soon as Tuesday afternoon.

"I'm an optimist. I put money on myself," McCarthy said on CNBC.

The leadership fight comes just days after Republican infighting took Washington to the brink of a partial government shutdown.

McCarthy's party controls the chamber by a narrow 221-212 majority, and it would take as few as five Republican defections to threaten his hold on power if all Democrats vote against him.

Democrats have not said whether they will vote against McCarthy or extract concessions to keep him in power. Many say they view him as untrustworthy after he broke an agreement on spending with Democratic President Joe Biden, and are angered by his decision to green-light an impeachment investigation of the president.

"I'm interested in hearing what every single member of the House Democratic family has to say on this issue. And then we'll come to a collective decision at the end," House Democratic Leader Hakeem Jeffries told MSNBC.

Jeffries said he had spoken with McCarthy on Monday night, but declined to say what was discussed.

Gaetz and other far-right Republicans are angered that McCarthy relied on Democratic votes to pass a temporary funding extension on Saturday that headed off a partial government shutdown. A faction of about 20 Republicans, Gaetz included, had forced McCarthy's hand by repeatedly blocking other legislation.

"If he's successful today, he'd be voting with all the Democrats. So you know what? It is what it is," McCarthy said of Gaetz.

Gaetz was one of more than a dozen far-right Republicans who repeatedly voted against McCarthy's bid for speaker in January. McCarthy ultimately secured the gavel after 15 rounds of voting.

(Reporting by Susan Heavy and Doina Chiacu; additional reporting by David Morgan; editing by Andy Sullivan and Jonathan Oatis)