US President Barack Obama has addressed reporters for the first time since the US election

President Barack Obama has taken a not-so-subtle swipe at President-elect Donald Trump.

Speaking to reporters for the first time since the Republican real estate mogul won the election, the outgoing leader wasted no time before making a quick dig at Mr Trump in his opening statements.

Mr Obama said he and his team stand ready to help accelerate Mr Trump's transition into the White House.

He said norms such as "civility, tolerance, reason and facts" are "vital to a functioning democracy".

He then said these norms will continue to be upheld "as long as I'm president". Ouch.

The opening dig wasn't lost on social media observers.

"As long as I'm president," the U.S. will uphold norms like peaceful transitions. -- @BarackObama . Interesting clause there.

— Domenico Montanaro (@DomenicoNPR) November 14, 2016

FINALLY Obama shows discontent. Civility, tolerance, fact, free press: "As long as I'm president" we will continue upholding these norms.

— Courtney Sender (@CourtneySender) November 14, 2016

Obama opening press conference: "As long as I'm president, we are going to uphold [civility] norms and cherish those...ideals." Subtweet!

— Eric Geller (@ericgeller) November 14, 2016

Mr Obama said his staff should be proud that he's left a country to Mr Trump to be proud of, saying "when we turn over the keys, the car's in pretty good shape".

"America has always been a pillar of strength and a beacon of hope to people around the globe," he said.

But he didn't deny that he was concerned, acknowledging the two leaders "differ on a whole bunch of issues".

"There are going to be certain elements of Trump's temperament that will not serve him well, unless he recognises them and corrects them," said Mr Obama.

"When you're a candidate and you say something that is inaccurate or controversial, it has less impact than it does when you're President of the United States. Everybody around the world is paying attention. Markets move. National security issues require a level of precision in order to make sure that you don't make mistakes.

"I think he recognises that this is different, and so do the American people."

He said he advised the incoming leader to think before he acts.

Barack Obama has said people have to give Donald Trump a chance before judging his presidency. Photo / AP

"One of the things I advised him to do was to make sure that before he commits to certain courses of action, he's really dug in and thought through how various issues play themselves out.

"I also think that he is coming to this office with fewer set hard-and-fast policy prescriptions than other presidents might be arriving with.

"I don't think he is ideological. I think, ultimately, he is pragmatic. That can serve him well, as long as he has good people around him and a clear sense of direction."

Mr Obama also told the crowds of people protesting the election result, it's time to move on and accept that the brash billionaire has won.

On the continuing rallies that have taken place across the country since the election results, Mr Obama said: "Those who didn't vote for Mr Trump will have to recognise that that's how democracy works.

"When I won, there were a number of people who didn't like me. They didn't like what I stood for. Whenever you've got an incoming president - particularly in a bitter election like this - it takes a while for people to reconcile themselves with that new reality. Hopefully it's a reminder that elections matter, and voting counts.

"I don't know how many times we have to relearn this lesson, because we ended up having 43 per cent of the country not voting, that was eligible to vote, and it makes a difference."

Mr Obama said it's too soon for the American people to cast judgment on the President-elect, saying they need to give him a chance to prove himself over his term.

"Given President-elect Trump is now trying to balance what he said in the campaign with his commitments to supporters ... I think it's important for us to let him make his decisions, and the American people will judge over the next couple of years whether they like what they see, and whether this is the direction they want to see the country go in.

President Barack Obama speaks during a news conference in the Brady press briefing room at the White House. Photo / AP

"I think he's sincere in wanting to be a successful president in moving this country forward. I don't think a president comes in thinking, 'I want to make people angry' or alienate half the country. I think he's going to try his best to make sure he delivers."

Asked about the advice he would give to the Democrats, Mr Obama said it will be a good thing for the party to be able to reflect on its loss.

"When your team loses, everyone gets deflated, and it's hard, and it's challenging. I think it's a healthy thing for the Democratic party to go through some reflection.

"I think it's important for me not to be big-footing that conversation. We want to see new voices and faces emerge, which is why I think term limits are a useful thing.

"I believe we have better ideas, but I also believe that good ideas don't matter if people don't hear them. One of the issues the Democrats have to be clear on, is, given population distribution across the country, we have to compete everywhere. We have to show up everywhere. We have to work at a grassroots level."

He also confirmed Mr Trump's commitment to NATO and the trans-atlantic alliance, following flip-flopping statements the Republican leader made on the alliances during his campaign.

Mr Obama said that he will be visiting with global leaders in coming weeks to "let them know that there is no weakening when it comes to America's commitment to maintaining strong and robust NATO relationship and a recognition that those alliances aren't just good for Europe, they're good for the United States".