Obama said he won't interfere or politically influence the investigation, which seeks to learn how much Clinton used a private email server while secretary of state. For months, the Department of State has been releasing thousands of pages of those emails.
"I guarantee that there is no political influence in any investigation conducted by the Justice Department, or the FBI, not just in this case, but in any case," Obama said." "Nobody is above the law. How many times do I have to say it?
"I've got to be careful because, as you know, there have been investigations, there are hearings, Congress is looking at this. And I haven't been sorting through each and every aspect of this. Here's what I know: Hillary Clinton was an outstanding secretary of state. She would never intentionally put America in any kind of jeopardy."
Clinton, the Democratic front-runner for president, has repeatedly denied transmitting classified information over a private server -- an assertion echoed by Obama on Sunday.
Clinton was secretary of state during Obama's first term, between 2009 and 2013.
"There's carelessness in terms of managing emails, that she has owned and she recognizes," Obama said.
Last week, the State Department announced it is halting its investigation into Clinton's email use so as to avoid interfering with the FBI's probe.
"Probably failing to plan for the day after what I think was the right thing to do in intervening in Libya," he said.
"I think that if they go through the process, they won't have a rationale to defeat him," he said.