North Korea sentenced this American student to 15 years in prison. How will US get him out?

Twenty-one-year-old Otto Warmbier is the American who's been sentenced by North Korea's supreme court in Pyongyang to 15 years of hard labor for "crimes against the state."

All for — North Korean officials say — attempting to steal a propaganda banner and subverting the government.

His imprisonment sets the stage for some delicate negotiations — and an attempt to bring him home.

Few know this dance better than Bill Richardson, former US ambassador to the United Nations.

“The first point you need to make is that we should separate this humanitarian release from the bad relationship that the US, South Korea, and China and the rest of the world have with North Korea. That's a very delicate task.”

Richardson is taking the lead on getting negotiations underway. The former ambassador and New Mexico governor is a veteran of talks with North Korea. He’s already met North Korean officials at the UN in New York to try to push for Warmbier's release.

“Secondly, you say to them, ‘look this is going to make you look good in the international community and you have a terrible image right now.’ So you have to be very frank with them but at the same time recognize that they're going to want something in return. They always use these detainees as bargaining chips.”

So what exactly might North Korea want in return for releasing Warmbier? What would sweeten the deal?

In this case like other previous cases, Richardson says, “they either want a high profile visit by an American, a former President Carter or a Clinton or the head of the CIA like last time to get another prisoner released or they want humanitarian assistance or they want to send a message. The problem is we don't know much about this new leader in North Korea. [Kim Jong Un] seems to be uncertain about his own situation in North Korea, his own power, so he’s a wildcard, we don’t know what he’s going to ask in return.”

Deputy Spokesperson @toner_mark comments on conviction of Otto Warmbier in #NorthKorea, urges #DPRK to pardon him. https://t.co/8WZ6RC5sGc

— Department of State (@StateDept) March 16, 2016

The extremely harsh sentencing comes as North Korea is politically isolated and faces a tough new round of UN sanctions following a nuclear test in January and a ballistic rocket launch last month. Meanwhile the US State Department accused North Koreans of using US citizens as "pawns to pursue a political agenda." But it could take months, or possibly years to negotiate Warmbier’s release.

“The good news, if there is any, is that after this 15-year sentence has been given to Otto Warmbier, now you can start negotiations.”

On the issue of whether publicizing these detentions will help or hurt negotiations for Warmbier release, Richardson is cautiously optimistic.

“I think it helps. If there’s more public pressure on North Korea and more actors get involved, I think that’s helpful. Of course official circles, the American government probably wants to keep this quiet as possible. But you can’t keep quiet that 15 years were given to a young man for a college prank," says Richardson. “North Korea has to make decisions on whether they want this bad publicity for detaining somebody on very dismal charges…but you never know what they’re going to do next, and that’s why this situation is so unpredictable.”  

 When last seen in public, Warmbier was being led from the Pyongyang court in handcuffs. He appeared to say something to the Swedish ambassador to North Korea who was on hand for the one-hour trial, asking him to "keep working" on his case.