JOHANNESBURG, South Africa -- President F. W. de Klerk claimed yesterday that South Africa "closed the book on apartheid" with the overwhelming tally of white votes in favor of bringing blacks into the country's political mainstream.
In a poll that defined the nation's course, white voters rejected appeals to return to apartheid and embraced the idea of a democratic society where blacks would also have a vote.
The poll was a major triumph for Mr. de Klerk, who had asked South Africa's 3.3 million white voters for a mandate to continue constitutional negotiations with the nation's 30-million-strong black majority.
It cleared the way for Mr. de Klerk to negotiate an interim government and a new constitution as part of a process that seems likely to move swiftly now that the referendum is over.
He predicted the vote "will give new impetus to the whole process of negotiations."
With a record 85 percent of white voters casting ballots in the crucial referendum, Mr. de Klerk received 68.7 percent of the vote, while the pro-apartheid Conservative Party received 31.3 percent.
His victory was bigger than most analysts had predicted, and it gave the South African president the landslide he needed to shrug off right-wing segregationist critics of his reform program.
"Today will be written up as one of the most fundamental turning points in the history of South Africa," Mr. de Klerk told cheering supporters in Cape Town.
Nelson Mandela, president of the African National Congress, was a little less reassured. He said the referendum did not kill apartheid or close the gap between blacks and whites in housing, education or medical facilities. "But it means a majority of whites are now prepared to address those issues."
The referendum result was not merely a mandate to Mr. de Klerk, he said, but to all parties involved in negotiations "to act with deliberate speed in order to realize an interim government that will prepare and supervise truly democratic elections."
Negotiations began in December between the government and 18 political organizations, including the ANC, which had been banned for 30 years until Mr. de Klerk legalized it in February 1990. Analysts believe the negotiations could result in an interim government before the end of the year and a new constitution sometime next year.
Mr. Mandela and other blacks had predicted a season of political turmoil, and possibly civil war, if whites had voted against the reform process. A wide spectrum of business and political leaders also said that South Africa would have been in for a new round of sanctions and international isolation if whites succeeded in turning back the clock.
The country still faces the prospect of violence from radical elements of the right wing, who are not expected to accept quietly the results of the referendum.
Conservative Party leader Andries Treurnicht said that whites would pay a high price for their referendum decision.
"The 'yes' vote will now have to pay its bill," he said in a bitter concession speech. "They will find out what it means to lose power and to have no power to defend your own freedom."
Mr. Treurnicht, who has accused Mr. de Klerk of turning over the country to Communists, said his party's struggle on behalf of the "white nation" would continue.
But the Conservatives' claim to speak for a majority of whites was discredited by the referendum results. The party lost in 14 out of 15 election districts, including three districts that were considered conservative territory.
The Conservative Party advocates the establishment of a white fatherland inside the present boundaries of South Africa. Radical right-wingers aligned with the party have threatened to go to war over the right to a special homeland where they would not have to live with blacks.
Analyst David Welsh, a political science professor at the University of Cape Town, said whites rejected the "crude racist populism" of the Conservative Party because they understood the consequences of a no vote.
"This was an absolutely crucial referendum, the most crucial in the country's history," he said. "I think most people got the message."
He said one of the main reasons whites voted with Mr. de Klerk was "a desperate desire to be regarded as part of the community of nations."
He said, "I think a lot of people are apprehensive about the future, but they thought a yes vote was a better bet than returning to the past."