William Perry served as US secretary of defense under President Bill Clinton from 1994 to 1997. After his tenure at the Pentagon, he observed Korean affairs up close while serving as Clinton's Special Envoy to North Korea. Perry is also the founder of the Perry Project, which aims to educate the public about the danger of nuclear weapons in the 21st century.

Days after the death of an American student who had been detained under the guise of having committed crimes against the regime, DW asks Perry for his take on the dangers posed by Kim Jong-un's unpredictable regime, the current diplomatic stalemate and whether there are any prospects for detente or even a unified Korea.

DW: Before the death of American student Otto Warmbier after his return from North Korea, you said that you see an opening for diplomacy with North Korea. Has Otto Warmbier's death changed your thinking?

William Perry: It has not, because I'd already believed that this regime was ruthless and the action they had taken with this hostage were very similar to the actions they have taken with the other hostages and to assassination attempts they made in South Korea. So if we are going into negotiation with North Korea, we have to do it with our eyes wide open. This is a ruthless, ruthless regime and we should understand that from the beginning. It's a ruthless regime that has nuclear weapons and we have to find a way of dealing with those nuclear weapons. My contention is that the only reasonable way to deal with them today is through diplomacy, and I do think we have an opportunity to succeed in diplomacy.

According to media reports North Korea's ambassador to India said the country is willing to talk to the US about a nuclear testing freeze, and China's foreign minister and South Korea's new president have also been pushing for new negotiations with North Korea in talks with US Secretary of State Rex Tillerson and Defense Secretary James Mattis. President Donald Trump recently seemed to close the door on trying to work with China on the North Korean issue while his secretary of state appeared to try to hold that door open. Do you think the Trump administration is speaking with one voice on North Korea and has a coherent strategy for dealing with the country?

President Trump has said contradictory things about negotiating with North Korea, so I don't take that as a guideline. I think the important thing is what the security team is saying. In this case, I think Tillerson and Mattis and possibly [National Security Adviser H.R.] McMaster are all interested in looking at the possibility of negotiations. So it's possible that they will come up with a negotiating approach and present it to the president.

Trump has said that all options are on the table. Do you see a preemptive strike, a military option, being a viable path forward?

I have myself - both when I was secretary of defense and, later, when I was advising the government - seriously considered preemptive strikes as a military option. But whether or not this was a good idea in those days, I am persuaded, I am convinced it's not a good idea today. A military strike would lead surely to a military response against the South and would do much damage to the South even with conventional weapons. It would likely involve the United States because we've got almost 30,000 troops over there, and it could all too easily escalate into a nuclear conflict. So I would not recommend a preemptive military strike at this time.

You have said that the US, under both the Bush and Obama administrations, never really had a negotiating strategy that made sense and could be successful. Why is that and what would a successful US negotiating strategy look like? 

First, I think they've never seriously considered the goals of the other side. North Korea's goal is to achieve the security for their regime, sustaining the Kim regime. And economic incentives, which we offered them, they'd like to have, but they would not do it at the expense of their regime, so all of their goal is to sustain the regime.

The Bush administration quite clearly was hoping for and pushing for a collapse of the regime. So that was not to be. The Obama administration had something they called strategic patience. I guess one interpretation of that is just, "be patient and wait until the regime collapses.” So to me that did not have a serious diplomatic approach which dealt with North Korea's goals, which were to sustain their regime, sustain the Kim dynasty. If we cannot do that, we might as well not waste time trying to negotiate.

What would a reasonable, realistic goal in possible negotiations be for the US now, since North Korea has these nuclear weapons that the six-party talks actually tried to prevent?

My goal, when I negotiated with them many years ago, was complete elimination of the nuclear programs and long-range missiles. And we had a shot at achieving that goal in those days.

Today the bar is much higher, because now they already have a nuclear arsenal and they are not likely to give it up easily. So today I think more how we still want to retain the goal of eliminating the nuclear weapons on the Korean peninsula, we have to do it in two stages. First stage would be to get a freeze on the nuclear weapons and their long-range missiles, and we can do that verifiably by controlling the testing. And the second goal then, once we have achieved that, would be to start a rolling back the nuclear weapons. So it's a complicated and slow process, but that's how we would have to approach it today.  

South Korea's new president will meet US President Trump for the first time next week in Washington. But next week also marks the anniversary of North Korea's attack on the South in 1950 which started the Korean War. The anniversary is also often used by North Korea to launch new missile tests. Do you expect another missile test next week, and how dangerous do you think the situation is now?

There will be more missile tests and more nuclear tests, but I don't have any idea what the timing will be.

Do you see that Europe, or even Germany, has a role to play in this conflict?

I think that at this stage, if the six parties are involved, it is sufficient. But when it gets to the stage where the nuclear problem is solved, and the question becomes one of unification, I think Germany's background and experience could be very useful in the discussion.

This interview was conducted by Michael Knigge.