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Mr. Dimon said he did not know the extent of the problem when he said in April that the concerns were a “tempest in a teapot.”

The loss came in the past six weeks. Mr. Dimon has said it came from trading in so-called credit derivatives and was designed to hedge against financial risk, not to make a profit for the bank.

Mr. Dimon told NBC that he supported giving the government the authority to dismantle a failing big bank and wipe out shareholder equity. But he stressed that JPMorgan, the largest bank in the United States, is “very strong.”

A piece of financial regulation known as the Volcker rule would prevent banks from certain kinds of trading for their own profit. Mr. Dimon has said the trading involved in the $2 billion loss would not have fallen under the rule.

Rep. Barney Frank, Massachusetts Democrat, told ABC’s “This Week” that he hopes the final version of the Volcker rule will prevent the type of trading that led to the massive loss at JPMorgan.

Mr. Dimon conceded to NBC that the bank “hurt ourselves and our credibility” and expects to “pay the price for that.” Asked what the price should be, Sen. Carl Levin, Michigan Democrat, said that banks will lose their fight to weaken the rule.

“We’ve got to be very, very careful that the regulators here are not undermined by this huge effort to weaken the rule by putting in a huge loophole” that includes the trading involved in the JPMorgan loss, he said.