By Richard Cowan

WASHINGTON U.S. House of Representatives Speaker Kevin McCarthy is staring down a threat to his leadership, which could plunge the Republican Party back into a crisis this week, days after dodging a federal government shutdown.

Rebellious Republican Representative Matt Gaetz on Sunday pledged to launch a bid to oust McCarthy as House speaker, just nine months after he struggled to win the job amid challenges from Gaetz and other hardline conservative Republicans.

"I am relentless and I will continue to pursue this objective," Gaetz told ABC, referring to a "motion to vacate" - the formal term in Congress for forcing a vote to remove McCarthy and trigger a battle for installing a new speaker.

McCarthy dismissed the threat from Gaetz telling CBS, "I'll survive." No U.S. House speaker has ever been removed from this high office that puts the holder second in line for the presidency after the vice president.

Gaetz was angered by McCarthy's move to pass a short-term funding bill on Saturday with support from opposition Democrats to keep the government fully operating. Gaetz and a group of other hardline House Republicans insist on deep spending cuts that Democrats argue would break a deal brokered earlier this year by President Joe Biden and McCarthy.

House Democratic Leader Hakeem Jeffries has not said if his caucus would join right-wing Republicans to help topple McCarthy or if Democrats might support him in exchange for political or legislative favors.

ONGOING BATTLE OVER SPENDING

The House and Senate now have until Nov. 17 to either agree to 12 spending bills for fiscal year 2024 or pass another stopgap measure to avoid shutdowns.

The Republican speaker and his leadership team are hoping to spend this week passing more individual spending bills to fund government programs in the new fiscal year that began on Sunday.

With only four of the dozen annual appropriations bills passed by the House before the start of this new fiscal year, House Majority Leader Steve Scalise, a Republican, has scheduled two more for debate this week.

It was unclear, however, whether the bills to keep federal energy programs operating and the lights on in Congress itself will garner enough Republican support amid a possible wall of opposition from Democrats.

Meanwhile, the Democratic-controlled Senate hoped to resurrect three bills that conservative Republicans blocked quick action on. They would fund federal agencies that run transportation, veterans, housing and agriculture programs that clash with the lower-spending priorities of Republican versions in the House.

Senate Appropriations Committee Chair Patty Murray also has placed a high priority on Congress delivering billions of dollars in new aid to Ukraine in its battle against Russia.

That funding was stripped out of the stopgap funding bill passed by Congress over the weekend amid Republican objections.

(Reporting by Richard Cowan; Editing by Cynthia Osterman)