South Korea's president expressed confidence Thursday that North Korea will abandon its nuclear weapons, after a summit with North Korea's leader at which the two countries pledged to pursue peace and end their decades-long standoff across the world's last Cold War frontier.

The leaders of the two Koreas signed an accord vowing to make "joint efforts to ensure the smooth implementation" of agreements made at six-nation arms talks "for the solution of the nuclear issue on the Korean peninsula."

"Now that the highest leader of North Korea has confirmed a clear commitment to the North's nuclear dismantlement, I don't see any problem in carrying it out," South Korean President Roh Moo-hyun said upon crossing the Demilitarized Zone by land after spending three days in the North for only the second-ever summit between the two countries.

"I firmly believe that the six-party talks will proceed well without any obstacles," Roh said.

At the arms talks with the U.S. and other regional powers in Beijing earlier this week, the North agreed to disable its main nuclear facilities and declare all its programs by the end of the year — which would be the farthest Pyongyang has gone to scale back its atomic ambitions in decades.

U.S. State Department spokesman Sean McCormack said Thursday that the six-nation negotiations were at the center of efforts to establish a changed relationship between North Korea and the world.

On Thursday, the two Koreas also "agreed to closely cooperate to end military hostility and ensure peace and the easing of tension on the Korean peninsula," according to the North-South summit declaration. The sides "shared the view that they should end the current armistice regime and establish a permanent peace."

Establishing a peace treaty would require the participation of the U.S. and China, which also fought in the fraticidal Korean War that ended in a 1953 armistice.

U.S. President George W. Bush said last month at a meeting with Roh that he was willing to formally end the war, but insisted it could only happen after Pyongyang's total nuclear disarmament.

Roh said he briefed the North's leader Kim Jong Il on Bush's willingness and Kim "expressed specific interest" in a formula to end the war that the South and the U.S. discussed. Kim "asked the South to make efforts to realize it," Roh said, without elaborating on the specifics of the plan.

"I've returned with the assessment that we can anticipate finally getting out of the half-century shackles of the Cold War and greet an era of genuine peace if the North-U.S. relations improve, along with the resolution of the North Korean nuclear issue, and if discussions on a peace regime begin in earnest," Roh said.

The lack of a firmer message on the nuclear issue in the North-South declaration drew criticism from South Korea's main conservative opposition party, which labeled the summit a political ploy to bolster the popularity of liberals aligned with Roh ahead of a December presidential election.

Roh, suffering from low popularity amid perceptions he has mismanaged the economy and security issues, leaves office in February.

"It's very regrettable that the South and North Korean leaders didn't take any substantial measures or show their firm commitment to nuclear dismantlement and peace on the Korean peninsula," the opposition Grand National Party said in a statement.

At a farewell lunch in Pyongyang on Thursday, the 65-year-old North Korean leader dismissed media reports that he was suffering from a range of ailments — reports that had drawn attention to Kim's public silence on his successor.

"South Korean media reported that I have diabetes and even heart disease, but the fact is that is not the case at all," he said.

After signing the final agreement of the summit, Roh seized Kim's right hand in his left and raised both their arms in the air like champion athletes.

The two Koreas also agreed to hold "frequent" summits, although no timetable was set. Instead, they scheduled meetings between their defense and prime ministers in the coming months to discuss issues raised at the summit.

Thursday's North-South accord calls for an expansion of economic cooperation, including establishing a new special economic zone on North Korea's west coast. They will also accelerate the development of an existing joint industrial park in the North Korean border city of Kaesong and start a regular cargo rail service there.

In an issue deeply emotional to many aging Koreans, the sides also agreed to increase reunions between relatives separated by the border. Since the first summit between the Koreas in June 2000, some 18,000 Koreans from separated families have met through face-to-face or video reunions.

They will also allow tourists to fly from Seoul to North Korea's tallest peak, Mount Paektu.

The North and South agreed that a joint cheering squad for the Koreas would travel to next year's Beijing Olympics via train. The countries have sought to field a joint team at international sporting events, but have differed over how athletes would be chosen.