A combative President Pieter W. Botha, puncturing expectations that he would announce major changes in South Africa's policy of strict racial separation, tonight delivered instead a defiant warning that he would not lead this country's ruling white minority "on a road to abdication and suicide."

While not ruling out the possibility of future reforms, Botha said he would not yield to pressure either from his government's enemies or from western critics into a sweeping overhaul of white rule and racial segregation here.

"We have never given in to outside demands and we are not going to do so," said Botha in his first major policy statement since he declared a state of emergency here last month to deal with rising racial unrest.

"South Africa's problems will be solved by South Africans and not by foreigners. We are not going to be deterred from doing what we think best, nor will we be forced into doing what we don't want to do."

Botha also issued a tough warning to those "militant revolutionaries" he said were instigating the unrest that has claimed more than 600 lives during the past year. He told them not to mistake for weakness his government's willingness to negotiate with those he called "responsible black leaders."

"I have applied much self-discipline in the past few weeks and months," Botha warned his foes. "I've been lenient and patient. Don't push us too far."

Reacting to the address, Anglican Bishop Desmond Tutu said world intervention offered the last hope of peaceful change in South Africa, Reuter reported. Tutu, winner of the Nobel Peace Prize and a prominent spokesman for black moderates, said, "I will say to (world leaders): We are intent on dismantling (the segregationist system) peacefully. Our last hope is the intervention of the international community.

"I hope President Reagan sees now the kind of person (Botha) he has been trying to protect. Here is a man who is refusing hands that are extended to him."

Even as Botha spoke, South African police were announcing new curfew restrictions designed to quell political violence in the eastern Cape and Johannesburg areas. Five more deaths were reported today, and new incidents took place in Soweto, the country's largest black urban center, which until now has been relatively free of the unrest that has gripped many other parts of the country.

Botha's speech was given to the annual provincial congress of his ruling National Party here, but it was clearly aimed at the West and at those he sees as his country's enemies. He made it almost entirely in English, despite the fact that the first language of most of the party faithful is Afrikaans, a local language based on Dutch.

The speech was warmly applauded here despite a handful of hecklers. It will likely be welcomed by many whites who feared the government might cave in to unrest and outside pressures, just as it is certain to be rejected by many black leaders, most of whom were not expecting major concessions.

Chief Gatsha Buthelezi, leader of South Africa's largest black tribe, the 6 million Zulus, said Botha's speech disappointed him and he found too little in it to stem the tide of violence. Buthelezi spoke to The Associated Press in Jerusalem where he is visiting.

The sharpest disappointment is likely to occur in Washington and other western capitals where diplomats had hoped Botha was planning to call for important new measures to dismantle apartheid. Leaked information from meetings last week in Vienna between South African Foreign Minister Roelof F. Botha and officials from the United States, Britain and West Germany had fueled expectations in the West and among South African newspapers.

The Senate and the House have both passed legislation imposing economic sanctions on South Africa unless the segregation policy, known here as apartheid, is relaxed. The Senate has yet to take action on the report of the conference committee. President Reagan, whose administration has followed what it describes as a policy of "constructive engagement" toward South Africa, has in the past said he would veto any sanctions. He has not, however, indicated what his intentions are regarding the current legislation.

Botha did not deviate from longstanding South African policy objectives nor from statements he made earlier this year about the country's political future.

He reaffirmed his government's commitment to establishing nominally independent "homelands" for most of its black citizens, although he also reaffirmed that the government would not compel such homelands to accept independence against their will.

He ruled out the unconditional release of jailed black nationalist leader Nelson Mandela, sticking to his statement earlier this year that Mandela would have to renounce violence before Botha would even consider freeing the man who has spent 22 years behind bars. "I repeat tonight what I said in Parliament and that is the end of the story," Botha said.

He rejected calls for one-man, one-vote democracy in South Africa, saying it would lead to "chaos." He also dismissed the idea of giving blacks a legislative house in the national parliament, where whites, Indians and persons of mixed race each have their own body.

Restating one of the main tenets of apartheid, Botha told his audience that there is no black majority in South Africa, despite the fact that 73 percent of the population is black. Instead, he contended, South Africa is "a country of minorities, white minorities as well as black minorities."

Botha also rejected calls that he make a statement of intent outlining the government's future course. "I am not prepared to make it, not now and not tomorrow," he said. "I am responsible for South Africa's future. I'm not going to walk into this trap."

The government has been widely perceived in recent months as vacillating between further reforms and a harsher crackdown as a means of quelling the intensifying unrest. The emergency declaration was a clear signal that officials had decided to stress the latter, at least temporarily.

Botha's speech, which followed a week in which at least 70 more people died in violence outside this port city and in scattered townships across the country, suggested it may move even further in that direction.

Botha gave no timetable for lifting the emergency, declared in 36 cities and towns, saying only that "any reduction of violence will be matched by action on the part of the government."

The speech did not even appear to go as far as Botha's opening address to Parliament last January, when he indicated plans for cautious changes in apartheid, including the granting of limited political participation to blacks living outside the homelands and the consideration of some form of national citizenship for all South Africans, including homelands residents.

Despite his hard-line approach, however, Botha in his hour-long address did not close the door on future reforms, pledging his government to "a program of positive action" and negotiations with representatives of other race groups.

He said South Africans of various races shared many values and that despite "important differences of policy . . . their love of South Africa is as intense as my own."

He made clear, however, that he would not be pushed into changes nor be seen acceding to pressure. And he accused foreign critics of encouraging revolutionaries with "comfort and succor."

Analysts struggled to explain why Botha seemed to have backed away from the reforms his diplomats in Vienna had suggested were coming. But the South African president himself seemed to offer the best explanation, telling his audience that he had interpreted the various leaks and prespeech speculation as a calculated campaign to trap him into fulfilling inflated expectations.

"I can recognize a skunk by its smell," said Botha, who later added, "It is of course a well-known tactic in negotiations to limit the other person's freedom of movement." He found such attempts "to compromise me and the government very unfortunate. It is a very dangerous game."

Reuter quoted government sources as saying the president's text had been revised four times in recent days. They said Botha did not want to be seen as bending to foreign pressure.

He directed much of his anger and scorn at the press, suggesting that journalists had misled their audiences into expecting too much from tonight's speech. Then he asked journalists to explain how they were "always present" when violence occurs in black townships. And he concluded by asking, to much applause, "Whose interests do you serve -- those of South Africa or those of the revolutionary elements?"

He blamed most of the country's recent violence on "barbaric communist agitators" who were "on the payroll of their masters far from this lovely country of ours."

The speech followed a day when police reported new incidents of unrest in at least eight areas in the Cape and Transvaal regions. Police announced tonight that they were extending new restrictions on townships in the eastern Cape and Soweto. Those include a nightly curfew from 10 until 4 and a ban on school boycotts by students.