The crash of South Africa's currency last week has shocked the normally apolitical business community into realizing that the system of white-minority rule has built weaknesses into the country's economy that make it vulnerable, economists here are saying.

"A complete shock has occurred," said Merton Dagut, senior executive of a major South African bank, Nedbank, in an interview today. "Businessmen were vaguely aware of the economic disadvantages of apartheid, but the closing of the foreign exchange and stock markets last week really focused their attention on the issue."

From now on, according to Dagut and other economists, business is likely to play a more assertive role in pressuring the government for political change.

In a development that lent support to this view, it was confirmed here today that a group of prominent businessmen is planning to hold talks soon with leaders of the underground African National Congress in Lusaka, Zambia.

One businessman involved in the proposed meeting, who did not want to be named, said today that several small groups already had held exploratory talks. He said no date had yet been set for the bigger meeting, "but it will be some time in September."

Announcing that it was willing to meet with the businessmen, a congress spokesmen, Tom Sebina, said in Lusaka last night that the African nationalist organization was willing to hold a dialogue with all sections of South African society that favored the abolition of the strict system of racial segregation.

People like Dagut, who have been in the forefront of opposition to the campaign for economic sanctions against South Africa, concede now that the campaign helped mobilize the business community into a political pressure group.

"The sanctions pressure has added to our accident-proneness, and to the extent that this shock has focused the attention of business on the root problem of apartheid, I guess it has done some good, although I don't think the sanctions campaigners knew the mechanism would work that way," Dagut said.

How the government will respond to political pressure from the business community is uncertain. Business does not have the same influence on government in South Africa that it does in the United States. Although changes have taken place in recent years, it is still mainly the preserve of the English-speaking minority, which historically has been in political opposition to the Afrikaner-dominated government.

Not only has this established a certain distance between the two, but businessmen tend to tread warily on political issues, fearing that if they antagonize the government they will lose valuable contracts with government departments and big semigovernmental corporations that control more than a third of the country's economic activity.

But many observers believe business' influence is potentially greater than it has been. President Pieter W. Botha has been courting business lately and is eager to draw it into a centrist alliance against the far-rightist Afrikaners who oppose his tentative attempts to adjust the apartheid system.

If the businessmen push him now, observers said, Botha will have some tough choices to make.

The point the economists are making as they examine the causes of last week's crash of the country's currency, the rand, is that the South African economy has been built on foundations of inefficiency and wastefulness related to its policies of racial segregation. These have been masked, however, by the income it is accustomed to getting from its enormous mineral wealth.

South Africa produces more than three-quarters of the noncommunist world's gold, which accounted for nearly half the country's total exports of $20 billion last year, and more than half its diamonds. It is also the world's biggest platinum producer and exports quantities of other valuable minerals as well.

A sharp drop in the gold price, which fell from $800 per ounce in 1980 to just over $280 earlier this year, together with a slump in other mineral prices, removed this mask, exposing economic deformities.

"We now see that we have an economy which has been accident-prone for some time," said Dagut.

The basic defect, said the economists, is that white South Africans, cushioned in their status of racial privilege, have grown accustomed to a "fat cat" existence that demands a large supply of consumer goods, while the apartheid system, by limiting black education and skills, has restricted the labor force available to produce them.

Added to this is an oversized bureaucracy needed to run an administrative system that provides parallel services for the segregated white, black, mixed-race or Colored, and Asian population groups. Some economists estimate that between half and two-thirds of South Africa's white manpower is employed by the state.

This has made for a society that lives beyond its productive means. As long as huge earnings from gold sales made up the difference, it went largely unnoticed. With the gold revenues sharply down, South Africa became a heavy borrower "simply to pay our living expenses," as one economist put it.

Growing international disapproval of apartheid and the campaign for American companies in particular to withdraw from South Africa have dried up investment capital coming into the country.

According to Finance Minister Barend du Plessis, the shortage of foreign investment capital has reduced South Africa's growth rate from a possible 5.5 percent to an actual 3.5 percent in recent years, a difference of more than $1 billion annually in the gross domestic product.

This has added to South Africa's need for foreign loans. Last year the government encouraged the borrowing of money abroad by arranging protection against unfavorable exchange rates for short-term loans.

That is how South Africa came to raise the large number of short-term loans that made it vulnerable to last week's financial crisis.

Dagut explained: "It was rational to borrow short-term rather than long-term, especially in the volatile Euro-market, with a broad expectation that sooner or later the dollar was going to fall and that interest rates were going to come off the peaks. There was also the hope that the gold price would go up again, strengthening the rand. So the shorter term the debt the better."

The result was that 67 percent of South Africa's current foreign debts of $16.5 billion are short-term, payable within the next six months.

"It created a situation where we had an accident waiting to happen," Dagut observed.

Economists agreed, however, that the accident was largely self-inflicted. A series of hard-line statements by President Botha in the face of continuing racial unrest, the declaration of a state of emergency in July, Botha's rejection of a request from Nobel Peace Prize winner Bishop Desmond M. Tutu for a meeting to try to defuse the crisis and finally his failure to announce expected reforms in a speech Aug. 15 combined to cause a sharp loss of confidence in the country's stability on the part of banks. They already were under heavy political pressure to stop loans to South Africa.

One after the other, beginning with U.S. banks, then spreading to others in Europe, they refused to roll over the loans and demanded prompt payment.

South Africa could not meet all its debts at once, and as the pressure increased, the rand plunged 35 percent in 13 days to an all-time low of 36 cents last Tuesday.

That was when du Plessis closed the Johannesburg foreign exchange and stock markets, sent Reserve Bank Governor Gerhard de Kock to London, Washington and New York to try to negotiate a rescheduling of the loan repayments, and South African businessmen got the shock that set them thinking about their country's political system.