McCarthy conceded to weeks of pressure from hardliners and allies of former President Donald Trump by launching a formal probe of Democratic President Joe Biden. The move sidestepped as many as 20 House of Representatives Republicans opposed to the action by avoiding a floor vote that would likely have failed.

"We cannot use impeachment as a political weapon against every president," Republican Representative Don Bacon, a Nebraska centrist, said in a statement.

But even after the announcement, hardline Representative Matt Gaetz again raised the possibility of ousting McCarthy under the terms of a deal he agreed to become speaker, which gave any one member the power to call a vote for his removal.

Gaetz said the speaker could face multiple votes on motions to "vacate the chair" for failing to comply with a secret agreement that allowed him to become speaker in January.

"The path forward for the House of Representatives is to either bring you into immediate, total compliance or remove you," Gaetz said in a floor speech addressing McCarthy directly.

As Congress approaches a Sept. 1 deadline to avoid a government shutdown, House hardliners are now pressing McCarthy to avoid any short-term stopgap spending measure to keep federal agencies afloat that fails to include border security provisions and other conservative priorities.

Gaetz cited a long list of measures that said McCarthy had failed to bring forward, including a balanced budget, term limits, the full release of videotapes from the Jan. 6, 2021, Capitol attack, and a subpoena of Biden's son Hunter Biden.

Representative Chip Roy, who helped lead negotiations that led to the hardliners' January agreement with McCarthy, confirmed that the speaker had not moved forward on the items listed by Gaetz.

"We haven't done that. Period. Full stop. We haven't done what we agreed to do," Roy told reporters.

But the Texas Republican shrugged off questions about McCarthy's future as speaker, saying the focus now is on achieving hardline spending targets and pushing through measures to address the U.S. border with Mexico.

Another hardliner, Representative Clay Higgins, said the focus should be on passing appropriations bills that cut spending to a fiscal 2022 level of $1.47 trillion, $120 billion less than he agreed to with Biden in May. Centrist Republicans oppose cuts that sharp.

Asked specifically about a motion to oust McCarthy, Higgins said: "Let me say that my colleagues should have deep, deep reflection before they venture down that path."

But McCarthy remains under hardline pressure not only to enact Republican appropriations bills with deep cuts but to force the lower spending levels on the Democratic-led Senate, which has begun moving forward its own spending legislation.

"We call on the speaker to be a historic, transformational speaker that for once stares down the White House, stares down the Senate, and stands strong for the American people, and says 'No!'," Republican Representative Bob Good said at a news conference.

While most hardliners have been unwilling to make open threats about McCarthy's future, many have still made it clear how strongly disappointed they would be if he decided to avoid a government shutdown with support from House Democrats.

"It would be a sad day for the country if he does that," said Representative Ralph Norman, a prominent member of the ultraconservative House Freedom Caucus.

"The only way I know to describe it: a sad day for America."

(Reporting by David Morgan; additional reporting by Makini Brice; Editing by Scott Malone and Stephen Coates)

By David Morgan