Republican Party leaders in both chambers are facing a mini-revolt among freshmen and conservatives over the three-week spending bill that they negotiated with Senate Democrats.

The fight over funding the budget for the rest of the year has dragged on so long without a deal that conservatives in both chambers appear to have had just about enough, with a growing trickle of lawmakers willing to risk a government shutdown instead of voting for another short-term measure.

"In both chambers the natives are getting restless," said a Senate Republican aide, who added that both parties seemed stuck in the middle of a "ginormous game of chicken."

Conservative Republicans started coming out against the short-term deal Monday - unwilling to go home for another recess without something more significant than an additional $6 billion in spending cuts. Without an extension, a partial government shutdown will begin Friday at midnight.

Freshman Sen. Marco Rubio announced early Monday that  he would no longer support any short-term spending bills.

The Florida Republican blamed Senate Democrats for focusing on Federal Aviation Administration reauthorization and patent reform instead of debt reduction, and President Barack Obama for a lack of engagement.

"All this has led to a very predictable outcome: Washington politicians of both parties scrambling to put together two- and three-week plans to keep funding the government, while not fundamentally changing the behavior that has gotten us into this mess to begin with," Rubio said. "I commend the efforts of House and Senate Republican leaders to deal with this, but I did not come to the U.S. Senate to be part of some absurd political theater."

Rubio's statement came as several influential conservative groups, including the Heritage Foundation's political arm, the Club for Growth and the Family Research Council, came out against the three-week deal negotiated by GOP leaders and said they would score the votes in their annual legislative scorecards.

Senate Minority Leader Mitch McConnell acknowledged that his Conference is divided on the measure over the level of spending cuts and the lack of policy riders.

"I think we can stipulate that it's not going to be easy," the Kentucky Republican said at a press conference, but he predicted the measure would pass.

McConnell defended the short-term deal, arguing that the $6 billion cut over three weeks is in line with House plans to cut $61 billion through September.

House Republican leaders have dissension of their own to deal with before the vote expected today.

In addition to the conservative groups lobbying against passage, Republican Study Committee Chairman Jim Jordan announced he would oppose the measure.

"With the federal government facing record deficits and a mammoth debt hanging over our economy and our future, we must do more than cut spending in bite-sized pieces," the Ohio lawmaker said.

Rep. Jeff Flake, who voted against the House's full-year CR for not cutting enough spending, also said he would vote against the short-term deal. "How are we ever supposed to tackle the grave fiscal challenges before us like the debt ceiling, the debt, and the FY2012 budget when we just keep punting on FY2011 spending?" the Arizona Republican said in a statement.

And GOP Reps. Steve King (Iowa) and Michele Bachmann (Minn.) are separately trying to rally opposition because it does not include a rider defunding Obama's health care overhaul.

But the push for a shutdown showdown isn't sitting well with some freshmen.

Freshman Rep. Michael Grimm on Monday slammed tea party activists and the "extreme wing of the Republican Party" for mounting opposition to the stopgap bill.

In a statement released by his office, the New York Republican argued that demanding ideological purity is "not looking at the big picture, and the last thing we want to do is become like [Minority Leader] Nancy Pelosi in the last Congress, where it was 'my way or the highway.'"

Grimm's statement comes just two months after he joined a handful of tea-party-inspired freshmen and Bachmann at a press event following a constitutional lecture by Supreme Court Justice Antonin Scalia.

On Monday, Grimm pulled no punches.

"If we're going to do what we set out to do, we have to set realistic expectations, and cannot bow to the extreme right or left. Those views don't represent what's best for our country and they certainly do not represent the views of the majority of my district," he said in the statement.

House Republican leaders downplayed the rift within their ranks Monday, arguing that it has been created by frustration with the fact that Senate Democrats had not yet passed their own bill.

Speaking to reporters Monday, Majority Leader Eric Cantor said conservatives have a right to be frustrated.

"We hope that this will be the last time," the Virginia Republican said. "There is a lot of frustration about the inability of this place to produce results. We have, time and again, seen the Senate unable to put a bill on the floor that can garner the 60 votes."

A GOP leadership aide echoed Cantor's comments, arguing that, "Our guys want to make sure that there is some sort of good faith commitment that this isn't actually the strategy long term and that they're going to come to the table and negotiate with us."

The aide also said that even with some conservative defections, it shouldn't be a problem for Majority Whip Kevin McCarthy (R-Calif.) to muster the votes needed to pass the bill.

"In the end, I don't think so. But like any significant vote, there's a conversation that has to happen," the aide said.

Democrats, meanwhile, worried that the day's developments significantly increased the chances of a government shutdown sooner or later, but they contended that what they consider to be overreach by conservatives would pin the blame on Republicans.

Senate Majority Leader Harry Reid said Republicans had failed to show they are willing to compromise or offer any ideas for reaching a long-term solution. "If no budget passes and we cannot keep this country running, it will be clear which side will bear that burden," the Nevada Democrat said.

And Democratic Conference Vice Chairman Charles Schumer (N.Y.) blamed the far right for blocking a longer-term deal and urged Speaker John Boehner (R-Ohio) to abandon the tea party. "In order to avert a shutdown, Speaker Boehner should consider leaving the tea party behind and instead seek a consensus in the House among moderate Republicans and a group of Democrats," he said.

Boehner spokesman Michael Steel responded by accusing Schumer of "cynically scheming for a government shutdown because he thinks it will help his political party."