WASHINGTON  Outlining a far-reaching proposal on Thursday to rebuild the nation’s broken system of financial regulation, the Treasury secretary, Timothy F. Geithner, fired the opening salvo in what is likely to be a marathon battle.

“Our system failed in fundamental ways,” Mr. Geithner told the House Financial Services Committee. “To address this will require comprehensive reform. Not modest repairs at the margin, but new rules of the game.”

On the surface, both the lawmakers who listened to the Treasury secretary and the financial industry’s lobbying groups made it sound as if they completely agreed with Mr. Geithner’s call for what he described as “better, smarter tougher regulation.”

But in fact industry groups are already mobilizing to block restrictions they oppose and win new protections they have wanted for years. Even though Mr. Geithner carefully avoided specific details, laying out mostly broad principles for overhauling the system, financial industry groups are identifying issues they plan to pursue and lining up well-connected lobbyists and publicists to help make their cases.