South Korea says its first working-level military talks with North Korea in two years ended with no progress.
The Defense Ministry said Thursday that South Korea pressed North Korea to apologize for the deadly sinking of a South Korean warship in March and to punish those responsible. Forty-six sailors died.
Pyongyang has denied involvement.
The ministry said North Korea responded it cannot accept the result of an international investigation that found it was responsible for the sinking.
Earlier, Pyongyang vowed to strengthen its nuclear deterrent in response to what it called U.S. threats.
Officers from the two sides met in the truce village of Panmunjom in the Demilitarized Zone that divides the peninsula, the ministry said. They last held such talks in October 2008.
At the United Nations, North Korea's Vice Foreign Minister Pak Kil Yon said Wednesday that Pyongyang would continue to expand its nuclear arsenal in order to deter what it perceives as American and South Korean aggression in the region.
"As long as the U.S. nuclear aircraft carriers sail around the seas of our country, our nuclear deterrent can never be abandoned but should be strengthened further," Pak said.
The North has routinely issued similar announcements. The latest one came after North Korean leader Kim Jong Il this week appointed his youngest son, Kim Jong Un, as a four-star general and also gave him key political posts aimed at an eventual succession.
Kim Jong Il took over the communist country in 1994 after the death of his father, the North's founder Kim Il Sung.
North Korea earlier this month proposed the military meeting to discuss the western maritime border and anti-North Korean leaflets spread by South Koreans. Seoul's Defense Ministry would not confirm what was on the agenda.
The poorly marked western sea border, drawn by the United Nations at the end of the 1950-53 Korean War, is a constant source of tension between the two Koreas.
Seoul has repeatedly rejected the North's long-standing demands that the sea border be changed. The navies of the two Koreas engaged in three bloody skirmishes near the area in 1999, 2002 and 2009.
Military tensions have been high since the sinking of the South Korean patrol ship. South Korea and the United States say the vessel was sunk by a North Korean torpedo.
The talks also came as South Korea and the U.S. hold naval drills in the Yellow Sea off the west coast of the Korean peninsula, near where the South Korean ship sank.
The exercises are the second in a series of joint maneuvers focusing on anti-submarine warfare tactics, techniques, and procedures, according to the South Korean Defense Ministry.