“The president has talked on a number of occasions about ensuring that the money that taxpayers put up to rescue our financial system is paid back in full,” Robert Gibbs, the White House spokesman, said.

So has the Treasury secretary, Timothy F. Geithner, who has drawn criticism from both the left and the right as not being tough enough on Wall Street.

Representative Barney Frank of Massachusetts, the Democrat who is chairman of the House banking committee, said the president was required to seek recovery of any losses under the law that created the $700 billion financial rescue fund, known as the Troubled Asset Relief Program, in October 2008. The law did not spell out how to do so.

“I did know they were thinking about doing this and I encouraged them,” Mr. Frank said.

Mr. Frank and others in Congress said they did not know any details, and administration officials say no decisions have been made beyond the fact that a proposal will be in the budget. Mr. Obama has been meeting with Mr. Geithner and with Lawrence H. Summers, his senior White House economic adviser, to discuss options from the Treasury department. News of the decision to propose some kind of tax was first reported by Politico.

The 27-nation European Union called for a global transactions tax in December, and last November Prime Minister Gordon Brown of Britain proposed the idea at a meeting of the Group of 20 developed and emerging nations, saying revenue could be stockpiled to finance any future bailouts. But Mr. Geithner has said a transaction tax, on trades of complicated derivatives and other financial instruments, would simply be passed through to investors and other customers, and could put American companies at a competitive disadvantage.

Separately, Britain and France have proposed a large tax on financial executives’ bonuses. Last year the administration successfully opposed a House bill that would have imposed a substantial levy on executive compensation, and officials continue to argue that corporate shareholders, not the government, should determine pay policies.