North Korea has failed to attend high-level talks with South Korea, a week after the South welcomed hundreds of refugees from the North.
It was the biggest group of refugees to arrive in the South
South Korea said it was "regrettable" the ministerial-level talks had not taken place.
The North is still angry with the South for granting sanctuary to 450 refugees who had escaped via China and Vietnam.
It is unclear whether the row will affect ongoing, six-nation talks about North Korea's nuclear ambitions.
The inter-Korean talks, the highest-level exchanges between the two countries, were due to open in Seoul on Tuesday and run for four days.
Previous discussions have focussed on economic issues and tourism.
But the North Korean delegation failed to arrive.
North Korea gave no official reason for its decision, but last week it accused the South of a "planned kidnapping" after two plane-loads of North Korean refugees arrived in the South.
On Tuesday, North Korea's Foreign Ministry repeated the claim, saying Seoul, instigated by the United States, "took away hundreds of Northerners, mainly women and children,
to South Korea in groups after alluring them to Vietnam".
The North is also angry that the South last month refused to let its citizens fly to the North to mark the 10th anniversary of the death of Kim Il-sung, the country's founder.
Analysts are unsure how long North Korea will try and use the refugee issue to indicate its displeasure.
The next round of six-nation talks on the nuclear stand-off was scheduled for September, though little progress is expected ahead of the US presidential election.
Hundreds of North Koreans successfully defect to the South each year, fleeing a Stalinist state wracked by famine which is at loggerheads with the international community over its nuclear programme.
The South has been accepting more than 1,000 people a year from North Korea, who generally have been arriving in far smaller groups of three or four.
The number of refugees has been grown steadily in recent years, with 760 North Koreans arriving in the first six months of 2004, according to official figures.
The two Koreas technically remain at war since the bitterly fought 1950-53 conflict ended in a truce not a peace treaty.
Their border remains tightly sealed along the Demilitarised Zone, guarded by some two million troops on both sides.