Mr. Sanders, in no mood to wait, said the banks were bigger today than when taxpayers bailed them out in the financial crisis. “If we are serious about preventing another major financial crisis and ending the enormous concentration of ownership within the financial sector, we have got to stand up to Wall Street and break these banks up,” he said in a statement.

Mrs. Clinton, by contrast, urged that the regulatory process play itself out under existing law, starting with banks submitting new living wills. Next regulators should impose higher capital requirements.

“And if these banks don’t fix their problems over time, then regulators need to break them apart,” she said in a statement.

In the past, Mr. Sanders has called Mrs. Clinton too compromised to take on Wall Street because she has taken large donations from bankers as a candidate and was paid $675,000 for a series speeches to Goldman Sachs. He regularly needles her to release the transcripts of the speeches.

Mr. Sanders pledged in January to break up banks that are too big to fail — that is, so important to the economy they would need a taxpayer bailout — within one year of taking office. He wants to reinstate the Glass-Steagall law of the 1930s that created a wall between investment banking and retail banks. It was partly repealed under President Bill Clinton, which Mr. Sanders maintains helped bring on the Great Recession a decade later.

Mrs. Clinton has called Mr. Sanders’s proposals inadequate because the financial crisis was caused not just by banks collapsing, but by the failure of “shadow” financial institutions like AIG, an insurance company, and subprime mortgage companies like Countrywide, which went on lending sprees.

“If all you do is look at the banks, you are missing shadow banking,” she told The Daily News in an interview with its editorial board recently. Mr. Sanders also spoke with the New York paper’s editors, and in endorsing Mrs. Clinton this week they cited the Vermont senator’s lack of specifics on how he would execute his “shock-and-awe bank-busting campaign.”