In a development indicating that negotiations toward a regional settlement in southern Africa are under way again, South Africa announced today that it will hold a ministerial-level meeting with Angola soon to set a date for completing its troop withdrawal from that country.

The meeting also will seek agreement on a means for securing peace along the Angolan-Namibian border once the South African troops have pulled out and a joint commission that was set up to monitor their withdrawal has been disbanded, the South African statement said.

It added that technical experts from the two sides would meet soon to discuss the jointly owned Ruacana-Calueque hydroelectric project, which was abandoned when Angola gained independence from Portuguese colonial rule in 1975.

The statement said these decisions were taken at a meeting of the Joint Monitoring Commission held yesterday at Ngiva, an Angolan village located 25 miles north of the Namibian border where the South Africans halted their withdrawal in May.

The commission meeting, the first in several months, took place three days after Chester A. Crocker, the U.S. assistant secretary of state for African affairs, held talks with South African officials in Pretoria. Those talks are believed to have broken a deadlock in the search for a settlement of the multifaceted regional conflict.

South Africa and Angola had agreed to a disengagement pact at a U.S.-brokered meeting in Lusaka, Zambia, in February.

Under the Lusaka agreement, South Africa was to withdraw an invasion force that had penetrated 120 miles into southern Angola. The invasion had been aimed at cutting off the guerrilla trails of the South-West African Peoples' Organization, the Namibian insurgent movement.

In return, Angola agreed to prevent the guerrillas from crossing the vacated territory, and the Joint Monitoring Commission was established to ensure this.

The South African withdrawal was scheduled to take place in five stages and be completed by March 30. Four stages were completed before the South Africans halted at Ngiva.

Their official reason for stopping was that the guerrillas were continuing to cross the border region. However, observers in Pretoria say that South Africa's main concern was that no provision had been made in the Lusaka agreement for continued joint policing of the border after the withdrawal was complete.

South Africa feared that, once its troops were out, the Joint Monitoring Commission would disband and the guerrillas would be able to move unhindered toward the Namibian border.

Angola, say observers, was reluctant to agree to establishing a joint border patrol after the pullout, because it did not want to be put in a position of obstructing the Namibian independence movement indefinitely. It was willing to agree to joint border patrols only if South Africa would commit itself to a date when it would start implementing a United Nations-approved formula for Namibia's independence.

This brought the tangled issue back to the main obstruction: a joint U.S.-South African precondition that an estimated 25,000 Cuban troops in Angola be removed before Namibia can become independent. Differences over this controversial "linkage" with the Cubans have stalled the Namibian independence negotations for more than two years.

In October, after months of quiet U.S. diplomacy, Angola offered a proposal that held promise of a breakthrough on the Cuban stalemate.

Crocker arrived in Pretoria Nov. 15 to convey the Angolan proposal to the South African government. He left the next day with a South African counterproposal that is thought to be positive enough to get the stalled negotiations going again. A joint statement as he flew out indicated that a tripartite meeting between South Africa, Angola and the United States might be held soon.

Yesterday's meeting of the Joint Monitoring Commission, which seemed to be in response to the new U.S. initiative, took place as Crocker flew from Zimbabwe to Mozambique on the second leg of a shuttle around the African "frontline" states to brief them on the new developnments.