In one of the most significant calls for change here in recent history. South African Foreign Minister R.F. (PIK) Botha has urged-repeal of two controversial laws banning interracial sex - the Mixed Marriages Act and the Immorality Act.

Although admitting in a statement published today that the suggestion would not be received well by many of his peers in the Cabinet and the ruling National party. Botha said, "My personal opinion is that these laws are not necessary for our [white] survival."

The move, first suggested by Minister of Agriculture Hendrik Schoeman earlier this week, is perhaps the most meaningtul call for change in 29 years of Afrikzner domination, since it would remove a cornerstone of apartheid policy - segregation of the races.

The Mixed marriages Act of 1949 prohibits marriage across racial lines. The immorality Act passed in 1927 and prohibited extramartial sex by parties of different races although there was no mention of sex out-of-wedlock within a racial grouping. It was replaced in 1957 by a similar law prohibiting any sexual relations across racial lines.

Botha's backing also is an improtant indicator of the growing lift between Verligte (Afrikaans for "enlightened") and Verkrampte ("hard-core") members of the National Party over the issue of change in South Africa. After the Schoeman statement Tuesday night, the influential deputy minister of Bantu (black) administration. Andries Treurnicht, rebuked his colleague.

Treurnicht referred to the white paper issued last year, which said that keeping the two acts was "to the advantage of all the communities on the grounds of the balance it created on the social level."

Earlier this year Prime Minister John Vorster said repeal of the two acts "would not work out." And Connie Mulder, minister of information and interior, declared the sex laws would never be repealed.

A growing number of members of parliament, however, now feel that the legislation should be abolished, since repeal would probably increase support abroad and ease race relations at home. One legislator said last night that a vote on repeal would be close.

Botha explained that it is time for South Africans to answer honestly the difficult questions of the day, such as the importance of the two acts to race relations.

The move to repeal the laws has already been heralded by both moderates and conservatives. The moderate Johannesburg Rand Daily Mail editorialized about the Immorality Act:

"This odious law has done untold harm to our national reputation in the world, and it has caused untold human misery among whole families who have been touched by it.

"Yet never has a serious justification for its existence been offered - except an argument by the government that it protected black women from being lured into prostitution by white men."

And Louis Nel - member of Parliament from Pretoria, the heart of Afrikanerdom - quickly added his support, saying. "Whether we have an Immorality Act or not, it makes no difference to me. I do not need it. All my relations and friends do not need it, either."

Several moderate politicians were surprised by the Botha endorsement, which adds clout to the repeal effort.

One member of the Progressive Reform Party commented. "I never thought they would consider revoking these laws because of the precedent it sets. Once you do away with mixed marriages and immorality acts there's no stopping you.

"If you allow mixed marriages, then what do you do about separate housing, separate transportation, separate amenities? The laws are fundamental to apartheid, separate development. I'm very interested in seeing just how far this goes."

Both laws are still taken seriously by the government. Last year, according to the Institute for Race Relations in Johannesburg, 325 persons where prosecuted under the Immorality Act. The latest statistics show 199 persons were convicted and 98 are awaiting trial.

In calling for repeal at a National Party rally, Schoeman said, "I don't see how we can go on like this. We don't need an Immorality Act. We must be the only contry in the world with such an act."

Schoeman also urged his party to accept major changes, such as mixed sports at the national level and consolidation of the fragmented homelands - the nine tribal reserves they will become independent ministates over the next few years.

Schoeman predicted: "Nationalities will accept anything as long as it does not threaten their identity and these things don't do that."

The call for change is likely to sign further controversy within the National Party, which has become [WORD ILLEGIBLE] in recent months over the extent of change needed in South Africa.

Just last month a storm of debate broke when Minister of Sport and Education Pleter Koornhof called for a new system of government modered on the Swiss cantonal scheme - a plant that implies full political participation by blacks. The speech was condemned by Treurnicht and other [WORD ILLEGIBLE] members of the Cabinet.

None of the issues are likely to be tested, however, until Parliament reconvenes in January.