South Africa's last apartheid president, Frederik W. de Klerk, apologized to the nation's truth commission today for the "pain and suffering" caused by the disgraced system of racial separation. But de Klerk said that neither he nor his party authorized the assassinations, torture and other human rights abuses that were among the hallmarks of white-minority rule.

De Klerk, whose National Party created apartheid nearly a half-century ago, was president for five years before South Africa's first all-races elections in April 1994. He said apartheid governments, including his own, were forced to use what he called "unconventional actions and reactions" to fight the "revolutionary threat."

That threat, from the vantage point of apartheid leaders, was posed by the African National Congress and other parties that represented the aspirations of the nation's black majority -- first peacefully, later through guerrilla warfare.

The ANC, led by President Nelson Mandela, is now South Africa's ruling party. But the nation is still riven by deep racial and social fissures -- with whites controlling the economy, blacks the politics -- and the legacy of apartheid is ever present. The Truth and Reconciliation Commission, led by Archbishop Desmond Tutu, was convened to help South Africans cope with their past and, it is hoped, close the remaining divisions.

In sessions that began in April, the commission has heard stories of torture, kidnapping, maiming and murder, carried out over the years mostly by state security forces but also by anti-apartheid groups. The panel's mission is to investigate apartheid-era abuses and to apportion reparations and amnesties; it is also to compile an official history of the nation's long road from racial repression to majority rule. All political parties are submitting statements to the commission to explain their apartheid-era activities; the ANC is to make its statement Thursday.

At the same time, several trials stemming from apartheid-era events are underway in the courts, including that of de Klerk's former defense minister, Magnus Malan, on charges of murder and establishing a death squad. But de Klerk, who has previously defended Malan, mentioned neither death squads, which operated in secret police units, nor the bombs that killed anti-apartheid campaigners, nor the slayings committed by security forces.

What he offered instead was a reiteration of an earlier, qualified apology and a defense of his party's policies. De Klerk, a widely praised political leader who was bred in the apartheid culture of Afrikaners -- descendants of 17th-century Dutch settlers -- said he was not trying to defend apartheid, only to explain it.

Apartheid, the outgrowth of racist practices instituted here by British colonialists, lasted from 1948 to 1994. It included a labyrinth of laws and regulations intended to ensure the self-determination and well-being of whites while keeping the black majority subservient.

"Deplorable as it may seem now," de Klerk said, official white racial domination had been the order of the day in Europe's African colonies, as well as in southern U,S. states until the latter half of this century. But here, he said, with rising black rebellion and urban migration, the "impracticality" of the apartheid vision became evident only in the 1980s.

"Instead of providing a workable and just solution," he said, separate development "led to hardship, suffering and humiliation -- to institutionalized discrimination on the basis of race and ethnicity. Instead of promoting peaceful intergroup relations, it had precipitated a cycle of widespread resistance and repression in which unacceptable actions were committed on all sides. Instead of providing a solution, it had led to injustice, growing international isolation and to escalation of the conflict that had been smoldering since the 1960s."

The statement marks a dramatic change in de Klerk's views from the 1980s, when as education minister he upheld laws of racial separation; in 1989, during the early days of his presidency, he said in an interview with The Washington Post that "separate development" was not a mistake. But in 1990, faced with growing black opposition and international sanctions, his government legalized the ANC and other banned parties and released Mandela from 27 years of political imprisonment. In 1993, de Klerk and Mandela received the Nobel Peace Prize for their work toward civil reform.

After taking a junior role in the transitional unity government after the 1994 elections, de Klerk and his party withdrew in May and became the main opposition in Parliament. De Klerk maintains today, as he has in the past, that he hails from the 1980s reformist phase of apartheid begun by his predecessor as president, P.W. Botha. The two men helped pave the way for the demise of apartheid, but de Klerk said Botha had refused to cooperate in the statement to the truth commission. CAPTION: De Klerk testifies for the National Party, which created apartheid.