"Given the difficulty in relations between the two sides, (you) can say that the meeting is of great significance itself," he said at a press briefing.

It's expected to serve as a chance for maintaining momentum in dialogue between the neighboring countries and producing a breakthrough in efforts to improve their ties, Kim said.

Moon is expected to raise the problem of Japan's export restrictions against South Korea. The Abe administration launched the trade measure in early July in apparent protest at the Moon government's handling of a World War II forced labor compensation issue.

South Korea had decided to terminate a military information-sharing agreement with Japan, called GSOMIA, but suspended the move as Tokyo has agreed to resume related dialogue.

Speaking on background later, a Cheong Wa Dae official struck an upbeat on the outcome of the summit, saying, "Progress is bound to be made when heads of state meet."

The official said there seems to be "gradual progress" in working-level meetings on the trade issue between the two sides.

On disputes over how to compensate for Korean victims of forced labor during Japan's colonial rule, the official said it's uncertain whether it will be discussed in the Moon-Abe summit.

"Since the Japanese side may make an inquiry (during the summit), we will have to make a preparation," the official added, reaffirming Seoul's principle of seeking a "victims-centered" resolution.

Moon and Abe had their previous formal summit in September last year on the sidelines of the UN General Assembly session. In November, they had a brief "impromptu" bilateral meeting in Bangkok just ahead of the ASEAN Plus Three summit.

Moon and Abe are scheduled to visit Chengdu for an annual trilateral summit that will be hosted by Chinese Premier Li Keqiang.

Moon also plans to hold separate talks with Chinese President Xi Jinping on Monday during a stopover in Beijing en route to Chengdu.

During his two-day stay in Chengdu, meanwhile, Moon will participate in a "business summit" to be joined by business leaders of the three regional powers.

In the three-way summit, the eighth of its kind, which is to take place on Tuesday, Moon, Abe and Li will assess achievements in tripartite cooperation so far and discuss ways for further development, especially as the launch of their formal cooperative system marks its 20th anniversary in 2019.

They will also touch on regional and international security situations including the Korea peace process.

"In particular, President Moon plans to explain about our government's efforts for the complete denuclearization of the Korean Peninsula and establishment of permanent peace and request constructive contributions by China and Japan," Kim said.

China earlier announced that a potential free trade agreement among the three countries will be among the agenda items in their upcoming summit.

The countries' trade ministers are slated to gather in Beijing this weekend for a round of discussions on the matter.

Publicly, Cheong Wa Dae maintains a cautious and prudent stance on the envisioned FTA.

With negotiations under way, the three nations will continue talks with the goal of a higher-level opening of their markets, according the Cheong Wa Dae official, who spoke on the customary condition of anonymity.