In an effort to lay the groundwork for direct talks between President Trump and North Korean leader Kim Jong Un, CIA Director Mike Pompeo made a top-secret visit to North Korea over Easter weekend, The Washington Post revealed Tuesday. Acting as an envoy for Trump after he was nominated to be secretary of state, Pompeo met with Kim himself, according to my colleagues.

On Tuesday, Trump alluded to the meeting when he spoke of direct talks with North Korea “at very high levels.”

He tweeted early Wednesday that the meeting went “very smoothly and a good relationship was formed,” adding that details of the planned summit were being worked out.

It was unclear why Trump wrote in his tweet that the Pompeo-Kim meeting took place “last week,” even though Pompeo had headed to North Korea about three weeks ago.

The details of the Trump-Kim summit and what will be discussed remain up in the air, but here are three of the key issues:

Where will the summit take place?

Trump said Tuesday that five locations are under consideration for the summit between him and Kim. None of those potential locations is in the United States, according to him.

The search for the right destination may also depend on factors that do not usually constrain international talks: notably the possible lack of an appropriate form of transportation for Kim, as The Post’s David Nakamura writes. While the demilitarized zone between North and South Korea or nearby China or Russia would be possible locations, other analysts have suggested countries that have previously acted as intermediaries between the United States and North Korea, such as Singapore, Switzerland or Sweden. But there might be a problem:

That has raised a question about how Kim, who made his first trip since coming to power outside North Korea to Beijing in an armored train last month, would get there. If Kim took his own plane, stopping to refuel on the way to any summit could also prove embarrassing by highlighting the limits of the aircraft — and where to stop would be complicated, as well, given the number of countries that have put sanctions on North Korea.

What would denuclearization on the Korean Peninsula entail?

During his visit to Beijing in late March, Kim was quoted by China’s official news agency as saying that “the issue of denuclearization of the Korean Peninsula can be resolved, if South Korea and the United States respond to our efforts with goodwill, create an atmosphere of peace and stability while taking progressive and synchronous measures for the realization of peace.”

But it is unclear whether both sides interpret their aim to achieve a “denuclearization on the peninsula” in the same way. With Kim's remarks in March, he may also have been suggesting that he seeks security assurances from the United States and other nations with nuclear arsenals that could theoretically reach North Korea — a condition the United States would be unlikely to accept, given that this would probably entail withdrawing missiles from much of the Pacific region, as my colleague Anna Fifield recently summarized:

To some in Washington, “the denuclearization of the Korean Peninsula,” as Trump tweeted late last month, means Kim handing over his nuclear weapons and missile systems and allowing international inspectors to check that the regime is keeping its word.
To Pyongyang, it means something very, very different. It means mutual steps to get rid of nuclear weapons, including requiring the United States to take down the nuclear umbrella it has put up over South Korea and Japan. That is a difference in definition that could toll a death knell for the summit before it even starts.

A different question is whether Pyongyang will stick to its frequently repeated demand that U.S. troops would need to leave South Korea as part of a denuclearization deal. The U.S. military alliance with South Korea has been in place since the 1950-53 Korean War, with about 28,000 troops now stationed in South Korea. U.S. troops there conduct regular joint exercises with their South Korean counterparts.

Will South Korea and North Korea be able to negotiate a peace deal?

Before the Kim-Pompeo meeting was revealed, South Korea said it was considering a peace agreement with North Korea. (The two countries are preparing a separate summit.) Both nations have emphasized their willingness to work on a deal in the past, but no detailed plans were ever negotiated.

A peace deal would replace an armistice that has been in place for decades and that essentially ensures a truce between both countries. North Korea and South Korea are officially still at war.

“People don’t realize the Korean War has not ended,” Trump said Tuesday. He voiced support for plans to strike a peace deal between the two countries but only if North Korea agreed to denuclearization.

How any such peace deal would really be negotiated is still unclear, however. South Korea itself is not a party to the armistice that was negotiated by a U.S.-led United Nations Command, the “Chinese People's volunteers” and North Korea. Hence, even if South and North Korea would want to announce the official end of the war, any such move would have to be preceded by complex negotiations in which the United States would have to play a key role. China would probably also want to have a say on any final agreement.

That may have been the point of the March meeting between Chinese President Xi Jinping and Kim, after which my colleagues Anna Fifield and Emily Rauhala noted:

“The message to the United States: Any moves on North Korea must go through Xi.”

More on WorldViews: 

Trump and the rest of the world offer little hope for Syrian refugees

Scientists can’t explain why diplomats in Cuba are suffering from ‘traumatic brain injury’

Buying ‘likes’ on Facebook is ‘immoral’, Egypt’s top Muslim cleric declares