Democratic presidential candidate Sen. Bernie Sanders declared during the recent Democratic debate that "the American people are sick and tired" of focusing on rival Hillary Clinton's "damn emails," but the Vermont independent changed his tune in an interview released Wednesday.

His comments during the debate were not meant to dismiss Clinton's use of a private email account and server during her four years as secretary of state, Sanders told The Wall Street Journal

There are "valid questions" to be asked regarding whether Clinton violated public-records requests or compromised classified information by using an unsecured email system, Sanders said, adding that the FBI's investigation into Clinton's email arrangement should "proceed unimpeded."

"You get 12 seconds to say these things," he told the WSJ, referring to his debate comments. "There's an investigation going on right now. I did not say, 'End the investigation.' That's silly. ... Let the investigation proceed unimpeded."

Sanders also spoke of his long-time opposition to the Trans-Pacific Partnership trade deal, an agreement Clinton once called the "gold standard" of trade accords but more recently came out against.

Weak consistency on such issues "does speak to the character of a person," he told the WSJ.

Sanders said another example is his 2002 vote against authorizing the U.S. invasion of Iraq, which Clinton voted in favor of as a New York senator, but now says was a mistake.

"It is important to see which candidates have the courage to cast tough votes, to take on very, very powerful interests," he said.

He then moved to Wall Street and financial reform, saying it's clear that he would be tougher on the issue than Clinton, who opposes reinstating Glass-Steagall, a law that separated commercial and investment banking, was repealed in President Bill Clinton's administration and then contributed to the financial crisis.

"I have been walking the walk, not just talking the talk," Sanders said, suggesting that Clinton has been compromised by the financial sector, which are among her largest sources of donations. "People should be suspect of candidates who receive large sums of money from Wall Street and then go out and say, 'Trust me, I'm going to really regulate Wall Street.'"