President Obama said there has never been "any man or woman more qualified" for the presidency than the presumptive Democratic candidate
Barack Obama has used a rally in North Carolina to show his support for Hillary Clinton as US president.
They were both on stage just hours after the FBI said no further action would be taken following an investigation into her use of a private email server when she was US Secretary of State.
The appearance in North Carolina is being seen as a show of Democratic unity.
"I'm here today because I believe in Hillary Clinton, and I want you to help elect her to be the next president of the United States of America," Mr Obama told the crowd.
He also suggested: "There has never been any man or woman more qualified for this office than Hillary Clinton. Ever. And that's the truth."
Mrs Clinton said she is "very privileged" to have known the president "in many roles: as a colleague in the Senate, as an opponent in a hard-fought primary, and the president I was so proud to serve as secretary of state.
"But I’ve also known him as the friend that I was honored to stand with in the good times and the hard times - someone who has never forgotten where he came from," she added.
Yesterday, FBI director James Comey said they will not be recommending charges against Hilary Clinton over her use of a private email serve.
Mr Comey said the investigation had found "extremely careless" behaviour by Mrs Clinton and her staff.
It is even possible that "hostile" forces may have gained access to Mrs Clinton's personal email account, he said.
However, outlining the agency's findings at a news conference, Mr Comey concluded that "no charges are appropriate".
It came after Wikileaks took to Twitter to announce that they would be releasing over 1,200 private emails from Clinton's personal server.