Mr. Dodd and others say that the market crisis last year was caused in part by banks that were able to choose which agency would regulate them, and by bank agencies that reduced regulations to encourage more banks to choose them.

That problem would be eliminated if there were only one bank agency.

The Dodd plan is certain to run into sharp resistance from banking industry lobbyists, who have already been urging lawmakers to defeat it even before it is formally introduced.

It is also likely to face stiff opposition from bank regulators, who are protective of their turf and have already raised objections about the more modest Obama plan.

Image Senator Christopher Dodd, chairman of the Senate Banking Committee, wants changes in President Obamas financial plan. Credit... Alex Wong/Getty Images

Mr. Dodd, who faces a difficult re-election campaign in Connecticut partly because of the perception that he is cozy with the banking industry, decided two weeks ago to remain chairman of the banking committee rather than succeed his close friend, the late Senator Edward M. Kennedy, as head of the health committee.

Senior Democrats in Congress say Mr. Dodd may have to thread a needle as he publicly takes on the financial services industry  whose members have a heavy presence in Connecticut and are some of his biggest campaign contributors  while trying to project an image of independence from it to get re-elected. But as chairman, he may also have to make compromises with industry lobbyists to move the legislation through a chamber in which bankers hold political sway.

Mr. Dodd said he decided to remain chairman after conversations with the senior committee Republican, Senator Richard Shelby of Alabama. He said Mr. Shelby persuaded him that it would be possible to get bipartisan support for stronger financial regulation despite major disagreements between even the two senators.