WASHINGTON - In an uncharacteristically forceful tone, House Speaker John A. Boehner on Wednesday lambasted the conservative advocacy groups that helped bring his party to power, saying their opposition to a bipartisan budget proposal amounted to an effort to manipulate Republicans and the American people "for their own goals."

The rare outburst, a reversal of his past approach toward influential conservative groups, underscored long-simmering tensions between them and more mainstream Republicans.

The hard-line groups have bedeviled Boehner and his leadership team all year by opposing efforts to compromise with Democrats and influencing primary campaigns aimed at unseating establishment Republicans, whom they accuse of abandoning conservative ideals on government spending.

Boehner's words also reflected his apparent confidence that the recently announced $85 billion budget deal will be approved by the House this week despite attacks by conservative groups like Club for Growth and Heritage Action. Even if as many as 100 Republicans vote against it, as some predicted, Boehner is counting on Democrats to make up the shortfall.

Only weeks ago, Boehner sidestepped questions about the influence of the outside groups. Asked in late October how they were affecting his members, Boehner answered simply: "Pass."

Though tensions have been rising for the last two years, Republican leaders resisted airing the frustrations publicly. But on Wednesday, tensions boiled over. At a news conference on the budget plan, Boehner interrupted a question about the developing opposition from conservative groups to charge that they "opposed it before they ever saw it."

"They're using our members and they're using the American people for their own goals," Boehner said. "This is ridiculous. If you're for more deficit reduction, you're for this agreement."

The outburst was long in gestation, Republicans close to Boehner said, and stemmed in part from many of the groups' support for a strategy led by Sen. Ted Cruz (R., Texas) that triggered the government shutdown in October.

Congress' expected passage of the tentative budget deal - forged by Senate Budget Committee Chairwoman Patty Murray (D., Wash.) and House Budget Committee Chairman Paul Ryan (R., Wis.) - appears to have emboldened Boehner to let go of his previous cautiousness.

Thursday's expected vote on the budget agreement will serve as a key test. Heritage Action, one of the most influential conservative groups, has urged lawmakers to vote against it, and said it would consider their votes in its rating system, which can be an important factor in primary politics. FreedomWorks, the tea party umbrella group, and Club for Growth are also urging a no vote.