More than 250 black nationalist guerrillas using mortars and AK-47 automatic rifles attacked a South African army base in South-West Africa near the Angolan border, Foreign Minister Reolof Botha said today.

Botha said several army troopers were wounded in the Tuesday night attack on their northern base in Nkongo. He did not mention guerrilla casualties.

Botha said the "whole delicate edifice of agreement" regarding a peaceful transition to independence in the territory, also known as Namibia, was in danger of collapse because of the attack.

The attack came two weeks before the first contingent of a U.N. peacekeeping force of up to 7,500 troops is to arrive in the arid but mineral-rich territory, which has been administered by South Africa since 1920 under a League of Nations mandate since rescinded by the United Nations.

The U.N. peace plan, backed by the West and recently given the go-ahead by South Africa, calls for elections next September in which the territory's one million inhabitants, mostly black, will elect a government for an independent nation.

Guerrillas of the South-West Africa People's Organization have been carrying on a hit-and-run war against South Africa troops in the territory for 12 years, mainly from bases in Angola.

But SWAPO leader Sam Nujoma has said his organization is prepared to participate in the U.N.-sponsored elections and will field candidates for office.

Botha claimed Thursday that Nujoma is now "desperate" about his agreement to have SWAPO participate in the election because he is convinced the territory's inhabitants do not support SWAPO.