Edmund L. Andrews reported from Washington, and Louise Story from New York. David Stout contributed reporting from Washington, and Michael de la Merced and Zachery Kouwe from New York.

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Treasury Secretary Timothy F. Geithner has fired the opening salvo in what is likely to be a marathon battle to rebuild the broken system of U.S. financial regulation.

"Our system failed in fundamental ways," Mr. Geithner told the House Financial Services Committee on Thursday while outlining his far-reaching proposal. "To address this will require comprehensive reform. Not modest repairs at the margin, but new rules of the game."

On the surface, the lawmakers who listened to the Treasury secretary and the lobbying groups of the financial industry 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 that they oppose and win new protections that they have wanted for years. Even though Mr. Geithner carefully avoided details, laying out mostly broad principles for changing 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.

If history is any guide, Mr. Geithner's proposals will start an equally intense battle among the regulatory agencies themselves - including the alphabet soup of banking regulators, the Securities and Exchange Commission and the Federal Reserve - to stay in business and enhance their authority.

It took years to complete past efforts to change the regulation of the financial industry - to replace Depression-era laws that separated commercial banks from investment banks, for example, and knock down barriers between the telephone and cable television industries.

And those efforts were in some ways easier than the task confronting President Barack Obama and Congress today. Many of the past changes were really about deregulation, knocking down legal barriers that had prevented different segments of an industry from competing with each other.

By contrast, Mr. Geithner's plan is the first attempt in decades to drastically tighten restrictions on industry. It would create a new still-unidentified "systemic risk regulator" that would have the authority to scrutinize and second-guess the operations of banks like Citigroup or JPMorgan Chase, insurance conglomerates like the American International Group and other financial institutions that are deemed too big to fail.