NEW YORK, JUNE 22 -- Nelson Mandela said today that he was "too busy" fighting apartheid to worry about threats against his life after the disclosure that South African police had arrested 11 whites in a right-wing plot to assassinate him, President Frederik W. de Klerk and others.

But the leader of the African National Congress warned about such violence in a triumphant appearance at the United Nations, where he said some white apartheid supporters are arming themselves "to establish paramilitary groups whose stated aim is the physical liquidation of the ANC." Mandela said that "we cannot afford to underestimate the threat" posed by these "right-wing terrorists."

The 11 alleged conspirators had planned to have Mandela killed by a sniper at the Johannesburg airport when the black leader returns next month from his six-week overseas tour, according to an Afrikaans-language weekly newspaper. Authorities confirmed that the suspects were arrested last night and later released.

News of the arrests came on a day when Mandela charmed 150 business leaders at the World Trade Center, denounced apartheid as an "intolerable scourge" at the United Nations, met with anti-apartheid activists, taped interviews for television shows and stopped by two celebrity-studded fund-raisers.

His wife, Winnie, who bought three formal evening dresses at a Seventh Avenue showroom Thursday, taped an appearance on the "Donahue" show, spoke at a Bedford-Stuyvesant church and was honored at the Brooklyn Academy of Music.

The Mandelas are to fly to Boston Saturday before beginning a three-day visit to Washington Sunday.

Several Jewish organizations criticized Nelson Mandela for repeating his support of Palestine Liberation Organization leader Yasser Arafat, Libyan leader Moammar Gadhafi and Cuban President Fidel Castro in an ABC News interview Thursday. Mandela again lauded the PLO in his U.N. address today.

Top officials of the American Jewish Congress said in a statement: "We believe Americans generally will be disappointed by his notion that the terrorism and human rights violations of the Gadhafis, Arafats and Castros of this world do not matter, as long as they provide aid to the ANC."

New York Assemblyman Dov Hikind (D), who canceled plans to protest Mandela's visit here, was more pointed, assailing Mandela for what he called the "immoral glorification of individuals who practice and support terrorism."

Mandela said today in a PBS television interview that he was "astonished" by the controversy, noting that the PLO and Cuba had aided the ANC as early as 1960 while the United States had refused to do so. He said it was "totally unrealistic" to expect the ANC to join in "vendettas" against such allies "in order to advance the interests of the West."

Earlier, at the United Nations, Mandela, who spent 27 years in South African prisons, twice received long, standing ovations and was hailed for more than an hour in several languages. U.N. Secretary-General Javier Perez de Cuellar called him a "champion of freedom."

Speaking from the oval-shaped well of the General Assembly chamber, Mandela called apartheid "an indelible blight on human history" that treats blacks as "subhuman." He said it "has established its own brutal worth by the number of children it has killed and the number of orphans, widows and widowers it can claim as its creation."

Mandela thanked members of the United Nations Committee Against Apartheid for working "to secure my release and the release of other political prisoners from Pretoria's dungeons."

At a news conference, Mandela was peppered with mostly parochial questions on subjects ranging from the Irish Republican Army to Detroit pension funds that have invested in South Africa.

Asked about the 1975 U.N. resolution that equates Zionism with racism, Mandela said: "If Zionism means the right of Israel to occupy the lands of other countries, like the Golan Heights, the West Bank and the Gaza Strip, then I condemn that. But if Zionism means the desire of the Jewish community to have their own state, then I support it."

When the questioner, WNBC-TV newsman Gabe Pressman, tried to follow up, Mandela cut him off, saying: "I'm not arguing with you."

The ANC leader sidestepped a question about allegations that the Central Intelligence Agency was involved in his 1962 arrest. "Let bygones be bygones," he said.

When a black reporter asked whether he would be willing to meet with Nation of Islam leader Louis Farrakhan, Mandela said, "I am not quite fully familiar with him, but if you want to arrange an appointment, here are my bosses behind me," gesturing to a line of ANC officials.

Mandela, a onetime boxer, also chatted briefly at the United Nations with heavyweight Mike Tyson. Sugar Ray Leonard and retired heavyweight Joe Frazier also were in attendance.

Earlier, in the 106th-floor ballroom of New York's tallest building, Mandela welcomed a proposal by Peter Goldmark, head of the Rockefeller Foundation, to form a development bank that would channel international investments into South Africa when blacks reach a political settlement with the white-minority government.

"We look forward to the time when you will join hands with our people to form a partnership of freedom and prosperity," Mandela told the business leaders. He urged them to support continued U.S. economic sanctions against the Pretoria regime.

The American executives, many of whom represent companies with ties to South Africa, gave him a standing ovation.

"Just being in the same room with him was very exciting," said Preston Robert Tisch, president of Loew's Corp. and chairman-elect of the New York City Partnership, a group of business and civic leaders that co-sponsored the meeting. "Mandela softened the business community's attitude toward sanctions."

"The most striking thing about this, and I've been on Wall Street a long time, was how excited this group of businessmen and women were," said Richard Leone, chairman of the Port Authority of New York. "You don't see that very often."

Mandela linked the interests of business with the political stability that he said would follow the end of apartheid. Investors, he said, "should know . . . that the investment they make today, whether in the house they build, the child they educate or the savings they put into a bank, is not likely to vanish tomorrow because of some arbitrary government action or a social upheaval generated by continuing social injustice."

Although the ANC platform adopted in 1955 calls for nationalization of monopolies, banks and mines, Mandela said the organization is "sensitive" to investors' needs.

But Mandela said the country's wealth is "owned by the white minority, and the black majority has no access to those resources. What we want to do is redress that imbalance."

Mandela's tone differed sharply from a 1958 article in which he wrote that "American capital has been sunk into Africa not for the purpose of raising the material standards of its people but in order to exploit them. . . . This is imperialism in the true sense of the word."

Mandela said today that he did not remember the article but that his "impression" is that U.S. policy had changed and that he has "modified" his views.