Talks on southern Africa resume despite military clash. Gathering in New York is to set stage for more meetings this summer

Despite a major military clash in Angola between South African and Cuban troops June 27, representatives of those two countries will sit down today with American and Angolan diplomats in New York. ``The fighting hasn't stopped anyone from coming,'' says a well-placed United States official, ``and seems to have increased both sides' desire to negotiate.''

There is a lot of tough slogging ahead before these talks come to fruition, US officials say. But this will be the third round with all four parties present, about withdrawing Cuban and South African troops from Angola and Namibia. Momentum appears to be building.

In the two days of talks, specialists from the four countries will be drafting a set of principles to guide what may be an intensive series of talks through the summer. The US and the Soviet Union have set Sept. 29 as a target date for an agreed package on troop withdrawal.

During the last four-party meeting on June 24-25 in Cairo, South Africa and the Cuban-Angolan delegation exchanged comments on the troop withdrawal plans each had submitted.

A final accord would provide for the phased pullout of the 45,000 to 50,000 Cuban troops in Angola and the about 25,000 South African and auxiliary troops in Namibia. (Up to 5,000 South African troops have operated in southeastern Angola in recent months supporting the anti-government UNITA movement.) Namibia would receive its independence as part of the accord. Angola is demanding that all foreign aid to UNITA be ended before an accord goes into effect.

Just after the Cairo negotiating session, however, Cuban and Angolan troops clashed with South Africa forces defending a South African-run dam in southwestern Angola. South Africa reported 12 white South Africans killed (probably by a direct air strike) and claimed 300 Angolan and Cuban troops died, which informed sources say is probably exaggerated by a factor of four or five.

For the first time, Cuba and Angola have the military edge in the border area where the clash took place, these sources say. They interpret the recent sizable Cuban reinforcements sent into the region as an effort to give South Africa more incentive to negotiate seriously.

Inside South Africa, there is increasing questioning of their military involvement in Angola. Last week for example, an editorial in the news organ of the Dutch Reformed Church - the main Afrikaner church - asked whether South Africa's military presence in Angola is morally justified.