WASHINGTON (Reuters) - Tea Party conservatives -- those budget-cutting, anti-establishment activists who shook up the Republican Party last year -- have a message for congressional leaders: We weren't kidding.
The Tea Party won its first big victory in Congress on Thursday, forcing House of Representatives Republican leaders to make deeper spending cuts than they planned and setting up a showdown with the White House and Democratic-led Senate.
Earlier in the week, Republican leaders suffered a series of setbacks in House floor votes after a rebellion by the Tea Party members who helped carry them to a majority in November's elections.
The events highlighted the potency of the anti-authoritarian Tea Party movement, and underlined the difficulties House Republican leaders face in controlling their new ideologically driven members.
"The real fight here is between Republicans and Republicans, not Republicans and Democrats," said budget expert Stan Collender, a former congressional staffer.
"The question is at what point will the Tea Party folks be satisfied? I don't think anybody can tell that yet."
On Thursday, House Appropriations Committee Chairman Hal Rogers, a Republican, agreed to rip up his spending plan and deepen the proposed cuts in a victory for fiscal conservatives aligned with the Tea Party.
Rogers had warned the deeper cuts, which meet a Republican campaign promise to trim $100 billion from the budget that President Barack Obama proposed last year, could force airport closures, layoffs at the FBI and other harsh disruptions.
The cuts demanded by conservatives were a rebuke to House leaders and rising Republican star Paul Ryan, chairman of the House Budget Committee, who endorsed a more gradual approach.
But the Tea Party elected dozens of new members to Congress on promises of limiting government and cutting spending, and fiscal conservatives in the House said the deeper cuts were a necessary "culture change."
"In just six weeks, we have already dramatically changed the conversation in Washington. Instead of more spending and more interference, Congress is actually thinking about how to rein in spending and encourage private enterprise," said Republican Study Committee Chairman Jim Jordan.
The move set Republicans on a collision course with Obama and his fellow Democrats as they try to pass a spending plan for the rest of this fiscal year before a March 4 deadline.
Senate Democrats are likely to propose extending current funding levels at least on a temporary basis, and with Tea Party conservatives in no mood to compromise the threat could grow of a cut-off of funds forcing a government shutdown.
"They are blindly swinging a meat ax to the budget when they should be using a scalpel. Some of these House Republicans won't be satisfied with anything less than a shutdown of the government," Democratic Senator Charles Schumer said.
The willingness of newly empowered conservatives to buck their leaders was evident earlier in the week during two embarrassing setbacks on the House floor on legislation that Republicans leaders had felt was noncontroversial and would pass easily.
"I think what they are finding out it that it is easier to talk about cutting than it is to actually do it," House Democratic leader Nancy Pelosi said.
In the face of the Tea Party's power, Republican leaders in Congress and the party's potential candidates in the 2012 presidential election have gone out of their way to praise the movement.
"Today it's the Tea Party calling us to our senses," Republican House Speaker John Boehner told a gathering of conservatives in Washington on Thursday night, shortly after the spending decision.
Additional reporting by Andy Sullivan and Thomas Ferraro; Editing by Vicki Allen