The South African government struck back today at the Roman Catholic Church, which has recently become outspoken in its criticism of the policy of racial separation by threatening to decertify recently integrated church schools.

An education official said this morning that the first steps in deregistering the four schools would be taken this week unless the nonwhites were expelled immediately.

When the schools opened their doors to nonwhites last month, the government warned that they were breaking the law and gave them until this week to reply. The Southern African Bishops' Conference responded with a strong statement that it would not back down.

Any government move against the schools would be a major setback to religious, business and private groups attempting changes on their own.

Many South African liberals had earlier indicated that they felt the government could not afford to act against the Catholics, the country's third largest denomination. They number more than 1.5 million, of which 40 per cent are African.

But it now appears that the government intends to take a strong stand on school desegregation to discourage independent change that counters official apartheid, or separation of races, policies.

In a television interview last night, South African Prime Minister John Vorster acknowledged that "in certain senses" the situation in the country was worsening.

In view of the looming confrontation with the Catholic Church and in light of several other developments on the racial scene, Vorster's comment was viewed by some here as somewhat of an understatment. Those developments were:

A black detainee died early today after felling from a 10th floor window at police headquarters in what police called an escape attempt. He was the 18th African detainee to die in alleged escape- or suicide-attempts in less than a year.

A government official pledged that the white-controlled Bantu (black) administration boards would never be abolished despite increasing calls for greater black control of their own affairs.

A prominent labor leader called for emergency relief for the 580,000 jobless not receiving unemployment benefits, while a senior police official warned of possible trouble stemming from a rapidly growing black unemployment - now estimated to be more than 650,000.

In its account of the black detainee's death, the police department said the unidentified prisoner had tried to escape by going out a window on the 10th floor and moving along a narrow ledge. Police said he stumbled and fell.

But the fact that 18 detainees have died while in police custody since last March led a Johannesburg lawyer to comment:

The police have lost all their credibility on these escape-and suicide-attempt claims. We all know how closely detainees are watched. It is just too much to believe that so many have been able to get loose or find ways to kill themselves.

"And how many times have independent pathologists found strange bruises and marks that don't match up with the stories? This isn't going to ease the tension between blacks and whites any."

Black anger is also not likely to be appeased by today's statement from the deputy minister of Bantu (black) affairs, William Gruywagen, that the (White) administration boards (of black areas) have come to stay and there is no questions of their demise."

One of the key issues emerging from last year's racial disorders was the demand by Africans to gain administrative control of their segregated townships.

Another spark that could reiginite racial violance is the growing African unemployment resulting from South Africa's current recession. As Arthur Grobbelaar, general secretary of the Trade Union Council of South Africa, said today:

"The South African unemployment rate might not have reached crisis proportions by Western standards, but we lack any provision to insure at least the basic survival of people with no livelihood."

Grobbelaar called for emergency food rations for poor blacks and public works projects to keep unemployed men occupied. "We do not want more angry youths on our streets," he explained.

His plea was indirectly supported by Col. J.P. Visser, police chief in Johannesburg's sprawling black township of Soweto. Visser warned his superiors that African unemployment could lead to new waves of crime and racial violence, according to the rand Daily Mail newspaper.

(The World Council of Churches soid in Geneva, witzerland, that it planned to pull funds out of a Dutch bank, the Algemene Bank Nederland, unless it stops granting loans to South Africa.)