WASHINGTON — America's banks are still broken despite all their bailout billions, Treasury Secretary Timothy Geithner told rescue overseers Tuesday as they pressed him on when things will get better and how much it will cost.

A bleak new report estimated that U.S. banks and other financial institutions could lose a stunning $2.7 trillion in all.

How well is the mostly spent $700 billion federal bailout working? "To date, frankly, the evidence is mixed," Geithner told a congressionally appointed oversight panel.

Confidence in the program is wearing thin on Capitol Hill. Even bailout supporters are skeptical that Congress, weary of bankers' bonuses and still-scarce credit, would approve additional bank rescue money if requested.

Geithner's testimony signaled that the administration was not preparing to ask.

Wall Street was cheered by Geithner's assessment that "the vast majority" of banks could be considered well- capitalized. Bank stocks had slid on Monday but bounced back Tuesday.

Still, officials must do a better job in carrying out and explaining their efforts to shore up the financial system, the head of the oversight panel told Geithner.

"The sense of fear and uncertainty has not gone away, but it's been joined by a new sense of anger and frustration," said Elizabeth Warren, a Harvard University law professor.

"People are angry that, even if they have consistently paid their bills on time and never missed a payment, their TARP-assisted banks are unilaterally raising their interest rates or slashing their credit lines."

Of the $700 billion authorized by Congress for the Troubled Asset Relief Program in October, Geithner said about $110 billion is left. With about $25 billion expected to be repaid this year, the total available is about $135 billion.

Some banks are maneuvering to pay back some of the bailout money, unhappy with the strings attached. Geithner said that doesn't mean the government would necessarily accept the repayments.

These questions have to be first answered, he said: "Do the institutions themselves have enough capital to be able to lend, and does the system as a whole, is it working for the American people for recovery?" A series of "stress tests" are being administered to banks by the administration to help judge their financial health.

Geithner said that a combination of factors, including the crushing weight of bad loans and other toxic securities on their balance sheets, was feeding "uncertainty about the health of individual banks."