SEOUL, South Korea -- North and South Korea ended their first working-level military talks in two years Thursday with no progress as the meeting stumbled over the sinking of a South Korean warship blamed on Pyongyang, Seoul's Defense Ministry said.
The rare encounter came hours after Pyongyang vowed to strengthen its nuclear deterrent in response to what it called U.S. threats.
A team of international investigators concluded in May that a North Korean torpedo sank the Cheonan warship near the two Koreas' disputed western sea border in March, killing 46 sailors. North Korea denies involvement.
On Thursday, South Korea pressed North Korea to immediately acknowledge and apologize for the sinking and punish those responsible, the ministry said in a statement after the talks in the Demilitarized Zone that divides the peninsula.
"North Korea's responsible measures over the sinking of the Cheonan are a key to resolve the issue," the ministry said.
North Korea's state news agency reported on the talks late Thursday, saying the North's representatives called Seoul's allegation about the sinking a "cheap farce" that was "foolish" to even discuss.
South Korea also urged the North to halt military threats and provocations near the disputed western sea border, as well as the North's slander of South Korean authorities, the ministry said.
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.
North Korea responded that it cannot accept the result of an international investigation and reiterated its long-standing demand that its own investigators be allowed to go to South Korea to examine the results.
The North also called on the South to rein in activists who spread anti-North Korean leaflets. Pyongyang also claimed that South Korean navy vessels regularly violate the western sea border.
The North said inter-Korean relations depend on how South Korea handles the two issues, according to the ministry.
At the United Nations, North Korean 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 promoted his youngest son, Kim Jong Un, to 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.
The talks also come 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.
Separately, a South Korean civic group and labor union sent 100 tons of rice to the North on Thursday to help ease food shortages following devastating flooding and damage from a typhoon, according to the group, the Korean Council for Reconciliation and Cooperation.