South African President Frederik W. de Klerk, scheduled to meet President Bush here on June 18, yesterday postponed his U.S. trip indefinitely, partly to avoid controversy about whether he or black nationalist leader Nelson Mandela should be the first to visit the White House.

"Due to a controversy that has arisen in the United States as regards the possible timing of my visit in June, and also because certain important matters would require my personal attention during the next few weeks, I have decided to postpone my visit to the United States," de Klerk said in a statement released in Cape Town.

"President Bush . . . stands by his invitation, and I will follow it up later at a time when it can make a more positive contribution to our mutual relations," de Klerk's statement added.

U.S. and South African sources said it now seems unlikely that de Klerk will come here this year. Instead, the sources continued, he probably will wait for clearer indications that negotiations between his government and black groups can progress toward a new governmental system incorporating South Africa's various racial groups.

The sensitive protocol issue behind de Klerk's move arose earlier this month when U.S. officials revealed that de Klerk would come to the White House June 18 and Mandela, who is expected to be in this country from June 20 to June 30, would see Bush a few days later, probably on June 25.

The African National Congress and American black leaders charged that receiving de Klerk first would be a snub to Mandela, the ANC leader who was freed Feb. 11 after 27 years in prison. No South African head of government has visited the United States in more than 30 years, and many American civil rights leaders argued that Bush should not receive de Klerk until South Africa substantially dismantles its apartheid system of white supremacy.

Both de Klerk and Mandela said they didn't care which one got to the White House first. But controversy persisted over the invitations -- intended by Bush as a gesture toward reconciliation between South African blacks and whites -- and reports from South Africa indicated that de Klerk had concluded a visit would be counterproductive.

"From our perspective, we are willing to see either gentleman at any time," White House press spokesman Marlin Fitzwater said yesterday. "We're perfectly happy with them coming at any point . . . We have not tried to guide them, one way or another, in terms of timing."

Other U.S. officials, who asked not to be identified, said the administration made no effort to persuade de Klerk not to come. They said he apparently concluded on his own that the positive reception he received on his recent tour of Europe would not be repeated in the United States.

De Klerk could have expected a warm endorsement from Bush and Secretary of State James A. Baker III for his efforts to move away from apartheid, the officials said. But, they added, he and his advisers concluded that the official friendliness probably would be overwhelmed by noisy and even violent protest demonstrations.

De Klerk has been attacked as a traitor by white South African rightists who contend he has conceded too much to blacks while failing to win removal of sanctions and moral disapproval that isolate his country from the rest of the world. As a result, the officials said, de Klerk apparently decided he had nothing to gain by coming here when his efforts toward moderation would be scorned as inadequate, and when official praise for them would be overshadowed by the adulation certain to be directed at the charismatic Mandela.

Randall Robinson, executive director of TransAfrica, a private American organization that champions black African causes, hailed cancellation of the visit as a victory for anti-apartheid activists. Robinson, one of the planners for Mandela's seven-city U.S. visit, said:

"{De Klerk's} decision is also a testament to the power of U.S. public opinion in influencing the South African government. It underscores the fact that American pressure produces results and that the U.S. government should not let up until there is substantive progress in the dismantlement of apartheid."