Not everyone in Washington, D.C., is happy with the arrival of South Africa President F.W. de Klerk, the first South African leader to visit the United States in 45 years. Some private groups picketed and members of the Congressional Black Caucus canceled a meeting with de Klerk in case it might be wrongly interpreted as a kind of approval.

Yet it would be wrong-headed not to recognize that de Klerk has presided over some basic changes in South Africa. The country clearly has a long way to go before eliminating the evils of apartheid, but there are encouraging signs of progress, slow though they may be.President Bush, in a meeting with de Klerk, praised the South African president for changes in the apartheid system and said the United States ought to "assist and encourage" South Africa in its efforts.

That could be interpreted to mean the lifting of sanctions, but Bush quickly dispelled that notion. Sanctions were adopted in 1986 over President Reagan's veto and have specific requirements attached before they can be lifted.

Some of those requirements have been met, accounting for Bush's praise. They include the freeing of Nelson Mandela and some other political prisoners; the lifting of bans on democratic political parties, and entering into negotiations with blacks leaders on a new constitution.

Requirements still not met include canceling the state of emergency in Natal Province, the release of remaining political prisoners and repeal of the Group Areas Act and Population Registration Act that restrict where non-whites work and live. Those latter acts, while eased to some degree, probably will not be entirely eliminated until apartheid is eradicated.

Opponents of de Klerk's visit argue that elimination of apartheid is not moving quickly enough. But the situation is complex. De Klerk has white enemies as well as black ones at home. Instant dismantling of apartheid would lead to chaos. It's not just blacks vs. whites in South Africa; there are many different tribes of blacks. The black-on-black violence and power struggles sweeping through some townships are indicative of problems that must be solved.

A new political system and constitution must be worked out that can be accepted by all parties. Fear and distrust and impatience and resistance to change must all be merged into a functional society. That is a slow, painstaking goal, filled with obstacles and quandaries. It is not something that can be accomplished by a wave of de Klerk's hand.

Undoubtedly, it would be politically impossible to lift U.S. sanctions against South Africa at this moment, but a friendlier and more helpful attitude toward South Africa's good-will efforts can at least be given.

De Klerk deserves encouragement for the changes he has wrought. In his year in office, he has come a long way from the attitudes and positions held by his predecessors. He ought to be given credit for that and helped to find his way through the thicket of problems he still faces, rather than being criticized because events aren't moving faster.