— Kim Jong Un, North Korea’s leader, plans to formally announce his willingness to denuclearize his country when he meets with President Moon Jae-in of South Korea this month, an official from the South said Tuesday.

The statement is expected to be part of a joint declaration that the two leaders will adopt when they meet on April 27, said Moon’s chief of staff, Im Jong-seok. Negotiators from both Koreas have agreed on a rough framework for the joint declaration, he said.

They are still discussing other aspects of the joint statement, such as whether the two Koreas would commit to holding summit meetings on a regular basis, Im said. South Korea is also trying to convince North Korea that Moon and Kim should hold a joint news conference at the end of their meeting in Panmunjom, the so-called truce village on the inter-Korean border.

If necessary, Moon’s national security adviser, Chung Eui-yong, and his spy chief, Suh Hoon, will visit the North Korean capital, Pyongyang, again to resolve any significant issues before the summit meeting, Im said.

When Chung and Suh visited Kim last month as Moon’s special envoys, Kim told them he would be willing to discuss giving up nuclear weapons if his government no longer felt threatened militarily and its security was guaranteed.

“Although the special envoys have already confirmed a willingness to denuclearize, it will make a difference if the two heads of state will meet and more clearly confirm it and make it a formal statement,” Im told reporters Tuesday.

More talks are needed to determine how specific the declaration would be about denuclearization, said Im, who is in charge of South Korean officials preparing for the summit meeting. But he said the joint statement would be broad and fairly “abstract,” because any substantial deal on the North’s nuclear weapons must be struck between Kim and President Donald Trump.

Trump has said he plans to meet with Kim in May or early June to try to persuade him to dismantle his nuclear weapons program. Moon, whose envoys brought Trump the message that Kim wanted to talk, has tried to be a mediator between the American and North Korean leaders, viewing his own meeting with Kim as laying the groundwork for the more important one to follow.

North Korean and U.S. officials have also been holding talks in preparation for their leaders’ meeting, during which U.S. officials have said the North reaffirmed a willingness to discuss denuclearization. But it is still unclear what Kim would seek in return for abandoning nuclear arms, and whether those demands would be acceptable to Washington.

When Kim met with President Xi Jinping of China late last month, he called for a “phased” and “synchronized” implementation of any denuclearization deal. Under such an approach, which North Korea has sought in past talks about its nuclear programs, the North would dismantle its program in stages, with each met by an incentive like an easing of international sanctions.

Some American hard-liners reject such an approach, saying that the North has no real intention of giving up nuclear weapons and is only seeking relief from sanctions. John R. Bolton made that argument before Trump chose him last month as national security adviser.

According to South Korean officials and analysts, Moon hopes for a “comprehensive deal,” in which Kim commits to dismantling his nuclear arsenal and Trump reciprocates with security guarantees for the North, including normalized ties and a peace treaty with Washington.

“When our special envoys visited Pyongyang, the mood was not bad, and we understand that the North Koreans and the Americans are both engaged in sincere discussions, so we are optimistic about the inter-Korean summit,” Im said. “But we could face obstacles any time.”