Barack Obama warns Donald Trump: Anything you say can start wars

US President Barack Obama speaks during his farewell address in Chicago, Illinois, January 10, 1017. (Photo by AFP)

Outgoing US President Barack Obama has warned about the dangers that lie with the powers of the high office, as he prepares to pass the baton to his successor Donald Trump.

"You have to be careful because anything you say can move markets or start wars," he said in a wide-ranging interview with NBC on Friday.

Obama discussed the various ebbs and flows of his presidency, naming the 2014 mass shooting at the Sandy Hook Elementary School in Newtown, Connecticut, as his lowest point in office.

"My worst day as president was hearing that 20 six-year-olds had been shot in the most brutal way," he said.

Obama also talked about the challenges of boosting his popularity with the American people and lifting up the party in a divided Washington.

"I had trouble transferring my personal popularity or support to the broader cause of the Democratic Party," he said. "And I think that's a legitimate criticism.”

As the first African-American president, Obama touched on the challenges he faced in trying to narrow the racial gap in the country

"I think any talk of the post-racial America before my election was never realistic," he said. "I think that talk was not only naive but it created some problems down the road."

During the course of the 2016 presidential campaign, Obama had repeatedly warned the American voters that Trump was “unfit for office.”

President-elect Donald Trump speaks to reporters at Trump Tower in New York City, January 13, 2017. (Photo by AFP)

The president had also said that world leaders had expressed grave concerns to him about Trump’s bombastic rhetoric and policy proposals.

Trump oversaw one of the most contentious and divisive campaigns in modern US history.

The real estate tycoon, among other things, attacked immigrants, dismissed allegations of sexual assault, supported the use of torture and called for a ban on Muslims entering the country.

The billionaire businessman also rattled many NATO allies by suggesting that the US under his command would only protect those that have paid their fair share to the alliance.