North and South Korea struggled Wednesday to resolve differences over creating a joint fishing zone around their disputed sea border at a second day of rare defense talks in Pyongyang.

The border was the main sticking point at the meeting between South Korean Defense Minister Kim Jang-soo and his North Korean counterpart, Kim Il Chol, media pool reports from Pyongyang said.

"I felt our differences are big," the South's Kim said during the talks, according to pool reports.

The three days of talks were the second-ever meeting between defense chiefs of the Koreas, which remain technically at war. They are aimed at fleshing out agreements struck at a summit between the two countries last month.

Recent progress on nuclear disarmament in the North has given new life to reconciliation efforts between the two sides. North Korea has begun disabling facilities at its main nuclear complex in Yongbyon in return for energy aid and other benefits.

The top U.S. nuclear negotiator with North Korea, Assistant Secretary of State Christopher Hill, is to visit North Korea next week to inspect the disablement work at Yongbyon. He said Wednesday he is confident the Communist country will meet a year-end deadline to disable the reactor as agreed with the United States and four other nations.

"We are making progress, and clearly we have more to do but I think we are on schedule," Hill said in Tokyo, his first stop on a regional visit that also includes South Korea, China and North Korea. "This does not end the path to denuclearization, and we have a lot to do in the year ahead. But to get to that work, we have to ensure that this phase goes well."

At the summit last month, North Korean leader Kim Jong Il and South Korean President Roh Moo-hyun agreed to establish a joint fishing ground off the divided peninsula's west coast to resolve a long-running dispute over their sea border.

The sea frontier was demarcated by the American-led U.N. command at the end of the 1950-53 Korean War — without consulting North Korea — and the communist country has long demanded it be redrawn further south.

The dispute prompted deadly skirmishes between the two navies in 1999 and 2002.

South Korea has proposed that each side provide the same amount of area around the sea border for the joint fishing zone.

Later Wednesday, officials exchanged draft proposals but it will be difficult for them to produce any written agreement unless the sea border issue is resolved, pool reports said.

"Negotiations are proceeding slowly due to differences in basic positions on main issues," said Col. Moon Sung-mook, spokesman for the South's delegation, according to pool reports.

Another key issue expected to be discussed is South Korea's hope for a military agreement with the North on security arrangements for cross-border freight train service, set to start Dec. 11, as well as other reconciliation projects.

However, the two sides were unable to begin discussing the matter Wednesday because of the sea border dispute, the reports said.

Earlier pool reports said North Korea argued that the South can achieve such agreements if it makes concessions on the sea border and other issues.

Without such an accord, the train service — which would be the first regular rail connection between the Koreas since the peninsula was divided more than half a century ago — cannot run.

The two Koreas' prime ministers met in Seoul earlier this month to follow up on the summit, and agreed on the freight train service and construction projects in the North. Amid the flurry of diplomacy, the North's spy chief was to make a three-day trip to South Korea beginning Thursday.