South African President Frederik W. de Klerk arrived here yesterday seeking support for his efforts to reform his country's system of apartheid and to establish a personal rapport with President Bush.

De Klerk cited the aspirations of the Rev. Martin Luther King Jr. in a brief speech at Andrews Air Force Base and said later, "We are proceeding irreversibly on the road to a new South Africa where justice, the guarantees of constitutional democracy and the rule of law will bring lasting peace and prosperity to all our people."

De Klerk said he will not press Bush to lift the U.S. economic sanctions imposed on South Africa in 1986 but "will inform him of the process of reconciliation that is taking place in our country."

Speaking on NBC's "Meet the Press," Secretary of State James A. Baker III described preliminary talks between de Klerk and South African black leaders as "very encouraging."

"I think we here in the United States should be encouraging those negotiations in every way that we can," he said.

De Klerk's three-day visit includes the first talks in 45 years between the presidents of the two countries. De Klerk and Bush are to meet today. De Klerk will also meet with congressional leaders, although the Congressional Black Caucus announced Saturday it had canceled a meeting with him, citing the recent violence in black townships that has claimed 750 lives.

Virginia Gov. L. Douglas Wilder (D), who is black, was scheduled to attend a dinner with de Klerk last night at Vice President Quayle's residence, a White House official said yesterday.

De Klerk spent most of yesterday in private meetings with his entourage and embassy staff. Several hundred anti-apartheid activists demonstrated outside the White House.