SEOUL, South Korea (AP) — South Korean President Moon Jae-in said Monday that he will push for "irreversible, permanent peace," and for better dialogue between Pyongyang and Washington, during "heart-to-heart" talks with North Korean leader Kim Jong Un this week. His chief of staff, however, played down the chance that Moon's summit with Kim will produce major progress in nuclear diplomacy.

Moon flies to Pyongyang on Tuesday for his third summit of the year with Kim. This one comes as global diplomatic efforts to rid North Korea of its nuclear program have stalled and questions have been raised about how serious Kim is about following through with his vague commitments to denuclearize.

"I aim to have lots of heart-to-heart talks with Chairman Kim Jong Un," Moon said during a meeting with top advisers, according to his office. "What I want to achieve is peace. I mean irreversible, permanent peace that is not shaken by international politics."

To achieve such a peace, Moon said he'll focus during the summit on easing a decades-long military standoff between the Koreas and promoting a North Korea-U.S. dialogue on denuclearization issues.

Moon said he wants "to find a middle ground between a U.S. request for (North Korea's) denuclearization and the North's request for corresponding measures such as ending hostile relations and security assurances."

During a June summit between Kim and President Donald Trump, the North Korean leader expressed his commitment to denuclearization while Trump promised to provide him with security guarantees and announced the suspension of major military drills with South Korea.

North Korea has long maintained that its nuclear program is aimed at coping with what it calls U.S. military threats. North Korea is pushing for a peace treaty with the United States to formally end the 1950-53 Korean War. It also wants the lifting of U.S.-led sanctions.

North Korea has taken some steps, like dismantling its nuclear and rocket-engine testing sites, but U.S. officials have said it must take more serious disarmament steps before receiving outside concessions.

Earlier Monday, Moon's chief of staff, Im Jong-seok, told reporters that it's "difficult to have any optimistic outlook" for progress on denuclearization during the summit. He said progress will depend on how candid the discussions are.

Im said he expects the summit to produce "meaningful" agreements that "fundamentally remove the danger of armed clashes and ease fears of war" between the two Koreas. He said the agreements will help promote chances for the signing of a peace treaty that formally ends the Korean War.

Military officials have in recent months discussed the possibility of disarming a jointly controlled area at the Koreas' shared border village, removing front-line guard posts and halting hostile acts along their sea boundary.

The Koreas' 248-kilometer (155-mile) border is the world's most heavily fortified, with hundreds of thousands of troops stationed along a line that's laced with mines, barbed wire fences and anti-tank traps. The navies of the Koreas have fought several bloody skirmishes off the west coast of the Korean Peninsula.

Moon will also take a group of business tycoons including Samsung scion Lee Jae-yong to Pyongyang. Some experts say Moon is preparing for the resumption of inter-Korean economic cooperation projects after diplomacy eventually yields results. Currently, all major joint economic projects between the Koreas remain stalled because of U.S.-led sanctions.

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