SEOUL, JULY 6 -- Communist North Korea said today it would open a small stretch of its border to promote unification with South Korea, but its capitalist rival dismissed the gesture as insignificant.

The Communist overture came as the prime ministers of the two nations prepared to hold historic talks, perhaps as early as August.

North Korea announced it would open the northern sector of Panmunjom, a border village, on Aug. 15, according to Naewoe Press, a semi-official South Korean news agency that specializes in Communist affairs.

North Korea said the opening, about 800 yards long and 500 yards wide, was aimed at promoting unification of the Korean Peninsula and urged South Korea to do the same, according to Naewoe.

"For successful progress of contact and visits between the North and the South, we will open the portion of our side . . . and hope that the south side will take a corresponding measure," the agency quoted Pyongyang as saying.

The opening, however, would not permit foreigners to travel inland, past the perimeter of Panmunjom, a truce village that straddles part of the 155-mile border.

The village is jointly controlled by North Korea and a United Nations Command, comprising the United States and 15 other countries that fought with South Korea in the 1950-53 Korean War. No civilians may enter the area from either side without approval.

South Korea's Defense Ministry said it had not been officially notified of the North's plans and would not comment on whether anyone would be allowed to cross the border. But a government spokesman said on condition of anonymity that North Korea's move was "insignificant" because it affected only a small, restricted section of the heavily fortified border.

Other officials said the move was intended to create divisions in South Korea, where dissidents are pushing for free contacts with the North.