South Korean President Moon Jae-in said Thursday President Trump and his North Korea counterpart, Kim Jong Un, need to move from “abstract” talk to “concrete” action the next time they meet, to speed up their peace process and bridge mistrust.

In an annual televised news conference, Moon said Kim’s trip to China this week suggests a U.S.-North Korea summit could be nearing.He added he expects news soon of high-level talks between officials from Washington and Pyongyang to plan for such a meeting. 

But he also called on Trump and Kim to “reflect” on the fact that their meeting last year in Singapore resulted in only an “abstract agreement,” using a Korean word somewhere between reflection, regret and self-examination. When they next meet, the two leaders should reach “clearer agreements on specific mutual measures,” he said.

Moon urged North Korea to be “bolder” in taking steps toward denuclearization. At the same time, he said, Washington needs to give Pyongyang some “encouragement.” 

“North Korea knows it needs to take clear denuclearization steps to see international sanctions lifted, and I think the United States also realizes that reciprocal measures are needed to match these North Korean denuclearization steps,” Moon said.

Moon has been working hard to mediate between Trump and Kim over the past year, and it is rare for him to express even veiled criticism of either man. But his government wants the peace process to move forward more quickly.

The South Korean president did not say exactly what steps he wants Washington to take, but he said he wants to see international sanctions eased as soon as possible to enable greater economic cooperation between the two Koreas.

Trump and Kim agreed in Singapore to establish new, peaceful relations between their two countries, while North Korea also promised to “work toward the complete denuclearization of the Korean Peninsula.”

Since that historic agreement, however, progress has stalled, with Washington frustrated that Pyongyang has not agreed to declare a list of its nuclear facilities, and North Korea displeased that the United States has done nothing to ease sanctions and signal a new era of peaceful relations.

In a televised New Year’s Day speech, Kim said he wants to fix the “unsavory” past relations between North Korea and the United States, is ready to meet Trump at any time and “will make efforts to obtain without fail results which can be welcomed by the international community.”

But he also warned he “may be compelled to find a new way for defending the sovereignty” of North Korea and achieving peace — if the United States breaks its promise by maintaining sanctions and demanding North Korea take unilateral steps.

Kim also said he wants to resume economic cooperation with the South “without preconditions” to reopen a joint economic zone in Kaesong and a joint tourism project in Mount Kumgang in the North.

Moon welcomed that commitment and said his government would cooperate with the international community, including the United States, “to resolve the remaining issues such as international sanctions as soon as possible” to allow both projects to go ahead.

He said it was wrong to suggest cooperation between the two Koreas would be a burden on the South’s economy, describing it as a potential “blessing” for his country’s business sector.

 Min Joo Kim contributed to this report.