US President Barack Obama
President Barack Obama has assured that the investigation into Hillary Clinton's emails will be impartial.Getty

US President Barack Obama has waded into the ongoing spat over Hillary Clinton's emails by arguing that the Democratic front-runner never endangered national security. Obama said that Clinton, his former secretary of state, had admitted being careless by using a private server to send and store official emails.

"I […] think it is important to keep this in perspective. This is somebody who has served her country for four years as secretary of state, and did an outstanding job," he told Fox News in an interview broadcast on Sunday.

Clinton's email arrangement between 2009-2013 – currently being investigated by the Justice Department – has dogged her campaign since it began. It stems from her use of a private server in contravention of FBI rules on storing classified information outside of secure government channels.

Clinton has repeatedly denied any malicious intent over using a private email server, but the issue has been leapt on by her Republican rivals, who have argued that she unfit for the presidency. They will hope to make as much of the issue as possible in the run-up to the US presidential election in November.

As well as the official investigation, two Republican-led Congressional committees are looking into the affair. The FBI has released tranches of the emails after seizing Clinton's private server.

Obama was asked whether he can assure a fair investigation given that it is being carried out under a Democratic administration: "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. Guaranteed. Full stop. Nobody gets treated differently when it comes to the Justice Department. Because nobody is above the law," he said.

Obama will leave the office of President of the USA on 20 January 2017.