U.S. House of Representatives Speaker John Boehner erupted in anger at conservative groups who oppose a rare bipartisan two-year budget deal on Thursday as lawmakers prepared to vote on the measure in the lower house.
The Republican Boehner said external groups had "lost all credibility" and stepped "over the line" by urging lawmakers to oppose the bill, which would avoid showdowns for about two years and mitigate some of the automatic budget cuts known as the "sequester".
Separately, a source close to Mitch McConnell, the Republican Minority Leader of the U.S. Senate, said he would vote against the measure if and when it arrives in the Senate next week.
(Read more: Cramer: 'Something up' with DC budget deal)
McConnell, who faces a challenge from a Tea Party conservative in his bid for re-election from Kentucky, opposes the deal because it would increase the spending level for government programs to about $1.012 trillion this year, up from $967 billion that had been previously scheduled.
The agreement itself appeared in little danger. It can probably pass the House and the Senate with a combination of Republican and Democratic votes.
The remaining question appeared to be how much public strife the budget deal would cause among Republicans at a time when they have been trying to draw attention away from their own ideological split and toward the failings of President Barack Obama's health care law.
(Read more: Cantor: Budget deal 'maintains savings')
Boehner, who has been going along reluctantly but quietly with Tea Party-oriented conservatives on most fiscal issues until now, blasted groups such as the Heritage Foundation, the Club for Growth and Freedom Works for egging on House members to oppose compromise both now and during the fall showdown that led to a 16-day partial government closure.
"They pushed us into this fight to defund Obamacare and to shut down the government. Most of you know, and my members know, that wasn't exactly the strategy that I had in mind," he said during a news conference.
"But, if you'll recall, the day before the government reopened, one of the people at one of these groups stood up and said, 'Well, we never really thought it would work'."
"Are you kidding me?" Boehner said, grabbing the podium and raising his voice for emphasis.
Asked if he was asking the outside groups to stand down, Boehner said, "I don't care what they do ... There just comes a point when some people step over the line."
(Read more: Budget deal a 'joke and betrayal': Stockman)
The deal promises to provide some relief from the automatic "sequester" spending cuts by increasing federal outlays by $63 billion over the next two years.
It shifts these cuts to other savings, including increased airport security fees and changes to federal pension programs, and offers up to $23 billion in additional deficit reduction over 10 years, mostly in future years.