President Barack Obama speaks at a rally for Hillary Clinton and Tim Kaine. Thomson Reuters Hacked emails from Hillary Clinton's campaign chairman revealed on Tuesday that the campaign panicked when President Barack Obama implied that he had no prior knowledge of Clinton's use of a private email server.

An email posted on the website WikiLeaks shows top Clinton aide Cheryl Mills' response when Clinton's traveling press secretary, Nick Merrill, forwarded a tweet that quoted Obama as saying he learned about the private server "the same time everybody else" did.

"We need to clean this up," Mills wrote to campaign chairman John Podesta. "He has emails from her — they do not say state.gov."

The exchange seemed to imply that Obama knew about Clinton's use of a private email server, which would contradict what he said during an interview with CBS News in March 2015.

When CBS White House correspondent Bill Plante asked Obama when he learned that Clinton used an email system outside the US government for official business while she was secretary of state, Obama responded, "The same time everybody else learned it through news reports."

The White House has addressed this supposed inconsistency. White House press secretary Josh Earnest said after the CBS interview aired that Obama "was referring specifically to the arrangement associated with Secretary Clinton's email."

"Yes, the president was aware of her email address," Earnest said. "He traded emails with her. That shouldn't be a surprise that the president of the United States is going to trade emails with the secretary of state. But the president was not aware of the fact that this was a personal email server and that this was the email address that she was using exclusively for all her business. The president was not aware of that until that had been more widely reported."

The FBI investigated Clinton's use of the server, but ultimately declined to recommend the Justice Department move forward with charges against her.