Lee Sang-hee of the Korea Research Institute for National Strategy, another co-host, said South Korea, the U.S. and North Korea "have different views in pursuit of their own interests when it comes to denuclearization of the Korean Peninsula." And Shin Beom-chul at the Asan Institute for Policy Studies, said, "Looking at the dialogue between the two Koreas last year, North Korea's position is to hold on to its nuclear weapons."

Experts predicted that Washington and Pyongyang will agree on a nuclear freeze rather than complete denuclearization at their second summit.

Jonathan Pollack of the Brookings Institution, which co-hosted the event, said diplomats from both sides are worried that North Korea will consolidate its status as a nuclear-armed state in talks with the U.S. backed by the South Korean government's dovish approach to the North.

The U.S. will probably accept that North Korea is a nuclear-armed state in the not-too-distant future, experts said at a two-day forum co-hosted by the Chosun Ilbo this week.

Evans Revere of the Brookings Institution said, "Washington's 'Plan A' -- engaging directly with the North Korean leader to convince him to denuclearize -- has failed. It is now time to think about 'Plan B' ...what several U.S. administrations have vowed never to allow: a permanently nuclear-armed North Korea." Revere instead called for "massive" sanctions and pressure on the North.

Participants forecast that Trump will make another unexpected concession at his next summit with North Korean leader Kim Jong-un that could strain the South Korea-U.S. alliance, much as he did during the first summit last year, when he unilaterally pledged to halt joint military drills with South Korea.

Park Won-gon at Handong Global University said, "I think it would be the worst-case scenario, but we cannot rule out the possibility of a unilateral removal of a Terminal High-Altitude Area Defense battery here."

Easing sanctions, which is among North Korea's key demands, will not be easy due to UN resolutions and U.S. laws, but redeployment of American strategic assets is in Trump's gift. "Trump's capricious decisions are well known, so close consultation between Seoul and Washington is necessary to prevent that," Park said.

And Shin added, "North Korea will focus on the subtle differences in opinion between [South] Korea, the U.S. and China on denuclearization, cross-border economic projects and the Seoul-Washington alliance, and attempt to drive a wedge into the alliance."

Bruce Klingner of the Heritage Foundation said policy differences between South Korea and the U.S. "were so great that it became impossible for them to remain out of the public eye." President Moon Jae-in seems to have tossed over the denuclearization task to the U.S. while he is focusing only on improving inter-Korean relations, he added.

Participants said inter-Korean agreements such as disarming soldiers in the border truce village of Panmunjom and dismantling guard posts along the border were of no help in denuclearization efforts.