Image copyright Win McNamee Image caption President Obama warned President-elect Trump about a threat to the US

Donald Trump said President Barack Obama had told him about a "big problem" for the US, but he wouldn't say what it was. What could it be?

"I was actually surprised a little bit," said the president-elect when telling New York Times reporters about his private conversation with the outgoing White House incumbent.

He said they had discussed "a big problem for the country", but refused to be drawn on the issue, telling journalists: "I'd rather have you ask him."

A reporter from the Times told me recently they haven't followed up on this matter with the president - not yet.

When I asked White House spokesman Josh Earnest about the issue, he said he couldn't reveal details of his boss' conversation.

Image copyright TIMOTHY A. CLARY Image caption Trump told New York Times reporters about Obama's advice

So I've turned to 10 experts - from the media, political science, government and other fields - and asked what they thought the president said during the important meeting.

North Korea and nuclear weapons

Ivo Daalder, president of the Chicago Council on Global Affairs, said: "My guess would be North Korea, which will likely be the biggest first crisis the president will face."

Thomas Karako, a senior fellow at the Center for Strategic and International Studies, said that he believes the president may have spoken about a shortcoming of his own administration - in the hope that, as Karako said, the new president may be able to address it.

Reporters at the Wall Street Journal agree, as they wrote about North Korea as the president-elect's most pressing issue in a recent article.

"Missiles are a big strategic vulnerability that crept up while the Obama administration wasn't looking," said Karako, explaining that as a consequence of the lapse the following has occurred: "Both provocations from North Korea that spook their neighbours, and also conspicuous Russian brandishing of nuclear weapons to bully Nato".

Foreign affairs

Bruce Jentleson, a political scientist at Duke University in Durham, North Carolina, said: "Cyber shutdown of utilities? Nuclear terrorism?" He jokingly added: "Or maybe the secret plan to make Taiwan the 51st state."

Image copyright Courtesy of Shamila Chaudhary Image caption Shamila Chaudhary says Obama may have warned the president-elect about Pakistan

Shamila Chaudhary, who served as director for Afghanistan and Pakistan on Obama's National Security Council, said that Mr Obama may have spoken about the region with Trump.

As she recalled, Mr Obama has "said on numerous occasions that the thing that keeps him awake at night is Pakistan, the growing power of jihadists on its territory and its nuclear weapons".

Current events

The New Yorker's Hendrik Hertzberg wondered: "The electoral college system, perhaps?"

Robert Kagan, a former Reagan State Department aide, joked: "Well, I was going to hold a seance tonight. But the first thing that came to mind was that the big problem was that the country just elected Donald Trump!"

Who cares?

George Mason University's FH Buckley, who's written speeches for Trump, is the author of The Way Back: Restoring the Promise of America. "I think the important thing is not what Obama wants but what Trump wants," said Buckley.

"The touchstone of the Trump campaign was: 'Make America great again.'" Buckley explained that Trump has a great interest in "economic mobility and economic opportunity" -and that he's likely to focus on these issues once he takes office.

Prisons

Time Magazine's Belinda Luscombe said: "Mass incarceration. Nobody wants to spend more money on prisons but it's like a leaky roof. If you don't fix it, it's going to keep costing you money to fix the damage it's causing to the rest of the house."

Image copyright ED JONES Image caption North Korea may be Trump's biggest issue - above, Kim Il Sung and Kim Jong-il portraits

A divided nation

Peter Mansoor, a military historian at Ohio State University in Columbus, said: "The biggest problem facing the country is the deep and persistent partisan divide that makes political compromise difficult if not impossible."

According to Melissa Michelson, a professor of political science at Menlo College in Atherton, California, the subject may have been "hate crimes, including incidents of racism, sexism, homophobia and Islamophobia that became more frequent during the Trump campaign and since Election Day".

No problem

George Washington University's Michael Cornfield said: "The 'problem' is a McGuffin, Hitchcock's term for an object that has no intrinsic purpose except to set the characters and the plot in motion.

"Trump wanted everyone at the New York Times to know he's now privy to the great secrets of the American security state."

While New York University's Charlton McIlwain, author of Race Appeal: How Candidates Invoke Race in US Political Campaigns, said he believes the following: "That he talked about one problem in particular could be an absolute fabrication.

"It would be perfectly in keeping with Trump's fantasy-is-fiction-is reality way of communicating with the public and the press."

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