Had things gone differently, Victor Cha, 57, could have been on hand to steer Donald Trump’s summit with North Korea on Tuesday.

Last year, the White House nominated Cha as its candidate for ambassador to South Korea. Diplomatic circles overwhelmingly welcomed the news. Cha, a moderate-right foreign policy hawk at Georgetown University, and a former nuclear negotiator with North Korea under the George W. Bush administration, had a reputation as a scholarly, steady hand who could instill sense in the mercurial Trump administration.

But hardliners in the White House and Defense Department had been entertaining talk of a “bloody nose strike” on North Korea—a limited, pre-emptive military attack designed to show the U.S.’s willingness to use force should North Korea continue building nuclear weapons. Cha publicly opposed a strike, writing in The Washington Post about the risk of “a rain of North Korean artillery and missiles” in South Korea.

Over this disagreement, the White House dropped him from his candidacy in January. Then, in a twist starting with South Korean-led diplomacy, Donald Trump agreed in March to meet North Korea’s leader Kim Jong Un, he called off the meeting on May 24, and resumed talks to set up a summit.

Trump will meet Kim Jong Un on June 12 at Singapore’s Capella Hotel, making him the first sitting U.S. president to meet a North Korean leader—and ironically, giving Trump a shot at a historic peace deal, if all goes well.

I sat down with Cha at the Center for Security and International Studies (CSIS), the security think-tank where he heads the Korea division, to discuss what this means for North Korea’s nuclear weapons program, how he’d advise the president, and whether he’s optimistic about the summit’s success.

The interview has been edited and condensed for clarity.

As a former negotiator with North Korea, if you could sit down right now with Donald Trump or Mike Pompeo, what would you tell them?

The first thing is that, obviously, peace is not a bad thing. Having said that, secondly, you should not want a deal too badly, and therefore should not put too many things on the table.

Third is that the goal must be denuclearization. To me, the clearest initial indicator of North Korean seriousness that this goes beyond where we’ve gone through in the past would be a complete, verifiable declaration.

The fourth thing would be that we want to make sure that whatever we do in the North Korea negotiation fits with our overall strategy and position in Asia, and does not undercut our alliances. If we become too enamored with technical negotiations with North Korea and we do things that hurt our alliances, then overall we’re not making ourselves more secure.

Examples of that would be starting to talk about American troops on the Korean peninsula, or not taking account of Japan’s concerns about North Korea’s short-range ballistic missiles.

When people in North Korea, South Korea and the U.S. say they want a “peace treaty,” what do they mean? Are we ready for that?

I think in general everybody wants the Korean War [of 1950 to 1953] to be over. The war has never ended. There’s only been a ceasefire since 1953. Then, given concerns about where we were heading in 2017 [with talk in of a pre-emptive military strike on North Korea], I think everybody would like to see this thing finally end.

But I don’t know if any parties are ready for a peace treaty yet. The South Koreans, I think, are not looking towards a peace treaty because that will then raise questions about U.S. troops on the peninsula, which South Korea sees as a very important sign of a continued security commitment from the U.S.

A peace treaty for the United States is very complicated. You’re talking about Senate ratification. If it were a peace treaty, then presumably China would have to be involved, because they were a signatory to the [Korean War] armistice.

What kinds of diplomatic gestures should we look for from North Korea at the summit?

Just the meeting alone, and the handshake, and the pictures will be enough for a lot of people. It was interesting to see President Trump smiling so broadly in the photo with Vice Chairman of the Workers’ Party of Korea Kim Yong Chol in the Oval Office when he was holding the letter.

You don’t really see him smile like that very often. It’s so bizarre to see him smiling so broadly next to the man who is partially responsible for putting 200,000 people in gulags and killing 46 South Korean soldiers in the North Korean torpedoing of the Cheonan naval corvette in March 2010, and hacking Sony Pictures Entertainment over the fictional depiction of Kim Jong Un in the 2014 comedy The Interview. Yeah, it’s pretty bizarre.

North Korea invited foreign journalists to witness the demolition of its nuclear testing site at Punggye-ri. Do you think that North Korea is really stopping its nuclear program?

I do think that whatever they did with Punggye-ri was really focused more on China than it was on the U.S., in the sense that the Chinese, I think, have been much more concerned about the location of the test site near the Chinese border. The last test, being the presumed hydrogen bomb test, actually created panic in the cities on the Chinese side of the border.

I do think right now they have stopped [nuclear] testing. But I don’t think they’ve stopped developing their programs at all. They have not made any commitments to stop developing their program. They could still be reprocessing plutonium. They could still be spinning centrifuges to create fuel for nuclear bombs. There’s nothing in what they’ve stated so far that should lead anyone to believe that they’re not continuing to develop their program.

On June 4, the conservative Chosun newspaper published an opinion article titled, “The U.S. Has Betrayed Korea At Times.” Opinions like these appear in left-leaning newspapers, but almost never in conservative ones. Do you think there is a changing political mood in South Korea towards the U.S.?

I think it’s natural as we get closer to this summit that South Koreans are going to be a little bit nervous, because President Trump is unconventional and unpredictable, and you just don’t know what he’s going to do.

There is the danger that if this doesn’t go well, the South Koreans might see the U.S. as an obstacle to inter-Korean engagement. Maybe that’s all part of North Korea’s strategy in terms of this. But I think once they get to the meeting they will proclaim it as some sort of success.

Are you optimistic about the summit?

I’m optimistic that the meeting will go well. I’m pessimistic that North Korea will fully denuclearize.