The Koreas' militaries were set to hold high-level talks on Wednesday that the South hopes to use to win approval for a scheduled test run of trains across the world's most heavily fortified border.
Two-star generals from both sides were to begin three days of meetings at the truce village of Panmunjom to discuss security arrangements for the rail test- a historic event that would mark the first time trains cross the border in more than a half century.
The two sides agreed to conduct the test run on May 17 at economic talks held last month, but it cannot happen unless the North's military gives its consent by agreeing to security arrangements.
Last year, the North's military called off a planned border crossing by train at the last minute, citing the South's rebuff of its long-standing demand that their western sea border be redrawn.
North Korea doesn't recognize the current sea border, demarcated by the United Nations at the end of the 1950-53 Korean War, and has long claimed it should be further south.
The waters around the border are rich fishing grounds and boats from the two Koreas routinely jostle for position during the May-June crab-catching season. In 1999 and 2002, their navies skirmished killing several sailors and sinking six ships.
There have been positive indications the North's military is likely to agree to the test run this time.
This week's talks are the first military contacts between the two sides in a year. The two Koreas remain technically at war since the 1950s conflict ended in a cease-fire, not a peace treaty.