After a 90-minute meeting with his successor, US President Barack Obama emerged from the Oval Office to say that he and Donald Trump had held an 'excellent conversation,' covering a wide range of issues.

The meeting marks the beginning of what Obama has vowed will be a "smooth" transition of power, despite their "significant differences."

After the meeting Obama said to Trump, "We now are going to want to do everything we can to help you succeed, because if you succeed the country succeeds."

Trump reciprocated, saying that he looked forward "to dealing with the president in the future, including counsel."

Subsequently, during a White House press conference, the president's spokesman, Josh Earnest, clarified that the "excellent conversation" did not mean that the two men had narrowed their sharply conflicting views on a wide range of issues, nor was that the intent of the meeting, he said.

"The meeting was focused on the transition and it went well," Earnest told reporters.

Trump's visit to Washington got off to a bumpy start earlier in the day when the president-elect refused to let journalists travel with him on his flight from New York, according to the Associated Press. The snub is a breach of the generally practiced protocol intended to ensure that the public has a watchful eye on the country's leader.

Obama has extended an olive branch to Trump and sought to steady nerves on the back of an embittered presidential election and arguably the most shocking election result in recent US history. Addressing disconsolate staff in the White House Rose Garden on Wednesday, the President adopted a conciliatory tone, saying that all Americans would now be "rooting" for Trump's success.

"We are Americans first," Obama said. "We're patriots first. We all want what's best for this country."

Trump similarly spoke of healing the deep divisions in a victory speech after leading a turbulent and often ill-tempered campaign.

However, today's Oval Office meeting may prove an awkward one. During the election campaign, Obama described the now President-elect as "uniquely unqualified" and said that he should not be trusted with the nuclear launch codes.

Trump, in turn, championed the so-called "birther movement" that challenged whether Obama was actually born in the United States – a suggestion laden with racial undertones.

White House spokesperson Josh Earnest had to downplay the commander-in-chief's rhetoric that painted Trump as an alarmingly ill-suited president. However, he declined to say whether Obama actually believed what he had said.

The celebrity businessman has also vowed to undo Obama's legacy. The Democrat ushered in sweeping healthcare reform and brokered a landmark nuclear deal with Iran. Trump has vowed to wipe away both those measures.

White House: Trump 'likely' to respect basic rule of law

In a warning that would seem unthinkable in almost any other election, both Obama and defeated Democratic candidate Hillary Clinton issued a faint but clear warning, urging Trump to respect the institutions and rule of law of the world's most foremost democracy.

At the Rose Garden on Wednesday, Obama said: "The country needs a sense of unity, a sense of inclusion, a respect for our institutions, our way of life, rule of law, and a respect for each other."

Earnest demurred when asked whether the White House believed Trump would live up to the requirement. His tone "would seem to suggest that certain basic principles of our democracy are likely to be upheld," he said.

As president-elect, Trump will be entitled to receive the same intelligence briefings as Obama. This includes information on covert US operations, information garnered from foreign leaders and data gathered from America's 17 intelligence agencies.

Trump will officially take office January 20.