From his second-floor office at the embassy, South African Ambassador Bernardus G. Fourie looks past the open curtains to Massachusetts Avenue. Through the bare branches of a tree, beyond an occasional pedestrian bundled up against the cold, he has a perfect view of the statue of Winston Churchill outside the British Embassy across the street.

Fourie has no view at all of the antiapartheid demonstrators who are starting to assemble at the corner. A District law requiring 500 feet between demonstrators and embassy spares him that.

Out of sight. Not, however, out of mind.

Every day, the demonstrators gather. Every day, a predetermined number routinely approach the front door of the chancery, ask to speak to the ambassador and, just as routinely, are removed by police.

"They demonstrate between 4 and 6 p.m., my working hours," Brand Fourie says. "I never go home before then. While they demonstrate, I work. It's their business and it's my business."

For all his seeming indifference, Fourie's life has changed dramatically since Nov. 21 when three leaders of the Free South Africa Movement refused to leave his office, an action that signaled the start of the demonstrations.

It has made him, simultaneously, a pariah in the eyes of the demonstrators, a defender of the sanctity of diplomatic missions in the eyes of his peers and a new media personality. Where he once averaged one or two interviews a week, the embassy says he now averages that many each day.

And while the arrests have triggered a wave of negative public relations against the South African government that even its organizers could not have anticipated, they also have opened a forum for Fourie to state South Africa's side.

"I'm a little fellow, quiet by nature, who loves puttering in the garden and talking to my house plants," Fourie says. But he has not missed the opportunity to put forth his country's case in the best light.

He says it is not difficult to represent a country whose policies are under attack, but "the tragedy is that the type of policy that's called 'South African policy' -- and I say it very often -- is a caricature of the real policy."

To Fourie, "It's like putting up a dummy and shooting it down and then thinking, well, you've dealt with apartheid. The type of apartheid that's often portrayed in the press we don't like ourselves."

He prefers to portray apartheid in the sense of gains made rather than inequities still to be rectified. "South Africa, of course, is basically no longer a white government," he says. "It's now a government of whites, coloreds and Indians."

Says an embassy spokesman of the effect of the demonstrations: "People are interested in South Africa and not all of it has been to the disadvantage of South Africa."

Although the signs are subtle, Fourie's social and business relationships with his Embassy Row peer group are unavoidably influenced by South Africa's apartheid policy.

"It is an extremely unpopular policy," says a western European diplomat. "If you have a nice party, you don't think of the South African ambassador -- any more than you think of the Bulgarian, the Czechoslovakian or the Chilean ambassadors -- as bringing a lot of fun to it. For one thing, it might turn your party into a polemical debate."

Imperturbable on the subject, Fourie says he has never felt ostracized in Washington, either before or after the demonstrations, nor has he ever been aware at any time that his presence has been an embarrassment, either to a host or to colleagues.

"Oh, there might be people who resent us, but so many are friendly. There are so many pressure groups," he says, pausing. "I don't want to bring the word 'racial' into it because I'll be accused the next day of saying this country is racialistic, and I'm not saying that."

The ambassador of a southern African nation that has no diplomatic relations with South Africa says he and Fourie do not pointedly avoid each other when they are at the same diplomatic function: "We just seem to be in different groups."

A courtly man known to like American football and American-style cookouts, Fourie is also a devoted family man who prizes his private life with his wife Daphne, whom he married when he was a member of the South African delegation to the United Nations in 1962. Their two children, Gerhard and Nicolette, are university students in South Africa.

"I've got one philosophy. When you go home at night, then you're at home with your family. You can't be in your office 24 hours a day. If you are, you won't last," says Fourie, who has "lasted" longer than most in a business where there are seldom any second chances.

Fourie says that he and his wife have not lost "a single friend [over South Africa's political policies] . . . I can tell you that Washington is full of very, very friendly people. I've been in our Foreign Service since 1938 and in no other city in the world have we made so many friends in so short a time . . . You'd be surprised at the letters and telephone calls I get from Americans who encourage rather than blast us."

Asserting that he lives by the same rules of social etiquette that he always has, Fourie turns down invitations "because I can't go to more than one place at the same time." He says he has not curtailed his official entertaining because of the demonstrations, nor does his government's apartheid policy affect how he draws up his official embassy guest lists.

"It's got nothing to do with it -- we certainly invite blacks, we certainly invite black Americans," he says. "But you can imagine that if you invite people to dinner you invite your own contacts and people with whom you can have a discussion and a dialogue -- even like having people from the press." Mayor Marion Barry's office says it has no record that he has ever been invited to a function at the South African Embassy.

Black Americans whom Fourie has invited to embassy functions call him correct and hospitable. Washington attorney Clarence McKee says each time he has been at Fourie's embassy he has found him "willing to discuss all sides and listen to my point of view . . . Like any ambassador, his position is to represent his government, understand the point of view of people in the United States and relay it back to that government."

Sent to Washington in June 1982 at a time in life when other people usually retire, Fourie, now 68, was hailed by officials in both countries. Washington expected him to be a decision-maker as well as an ambassador. South Africa, which viewed his 16 years as foreign secretary as a plus with the then-fledgling Reagan administration, saw him playing a double role as Pretoria's negotiator on Namibia.

Highly respected at home, where he was regarded as the man who kept South Africa's Foreign Service together, he was known as the "consummate" diplomat, the negotiator's negotiator and "Mr. Namibia."

"He worked hard on Namibian independence negotiations," says a friend. "The world's agenda for South Africa in the late 1970s and 1980s was peace with Mozambique and Angola, independence for Namibia and an adjustment of domestic reforms away from apartheid. They were Brand's principal activities so he stayed on, and he came here because they were getting very close [to fulfilment]."

Former U.S. ambassador to the United Nations Donald McHenry, chief U.S. negotiator on Namibia during the Carter administration, remembers Fourie, then South Africa's secretary for foreign affairs, as "a real professional who is honest, aboveboard, knowledgeable and never played games."

McHenry's disagreements with the rambunctious and volatile Roelof F. (Pik) Botha, South Africa's foreign minister, were as well known in Pretoria as they were in Washington.

"Fourie was the peacemaker," says McHenry, who is credited with setting in motion the U.N.-supervised plan for Namibian independence. "I always found it better to deal with him than with the foreign minister. When an impasse took place, it was to Brand's house we went, had coffee and worked it out -- frequently to the limit of his authority."

McHenry's impression of Fourie was that of a pragmatist "who tried to work through problems and had a sense of what couldn't be done now. He was totally dedicated to the policies of the South African government . . . You wanted to believe that he would be working for what could be in the future."

McHenry isn't the only one who has had that impression. "Beneath that icy exterior is a man who realizes how serious what's going on now is and knows what the [Reagan] administration is going to do but has problems getting that across to his superiors," says one source.

Fourie's problems communicating have made him vulnerable, in the eyes of some. "Unfortunately," says one source, "the American government has found he's not always in the know about what is going on in South Africa. When Herman Toivo ja Toivo, secretary general of South West Africa People's Organization, was released from prison after 16 years, the first Fourie heard about it was from a South African journalist."

Fourie was a prote'ge' of Jan Christiaan Smuts, South Africa's international statesman who worked closely with Woodrow Wilson on the League of Nations, was a founding father of the United Nations and was one of South Africa's more enlightened politicians. Fourie says his love of the United States, in fact, goes back to 1945, when he was a young diplomat accompanying Smuts to San Francisco for the organization of the United Nations. Only after Smuts' defeat as prime minister in 1948 did the government drastically begin to implement its policy of apartheid.

"I do not draw a line between a black American and a white American," Fourie says. "I find it useful to talk to any American who's prepared to talk to me constructively. I don't put on my glasses to see whether he's black or white. I've got nothing against black people or black Americans, as a person, none whatsoever."

So it was that he found himself, last November, holding a meeting in his office with Del. Walter Fauntroy, Free South Africa Movement cochairman Randall Robinson and U.S. civil rights commissioner Mary Frances Berry. The session had been postponed twice before, first because of the Rev. Martin Luther King Sr.'s funeral and then because of a business trip Fourie made to South Africa.

On television, Fourie and Robinson had previously debated South Africa's controversial policies of racial separation. The ambassador says he looked upon the embassy meeting as "a continuation" of their debate in which he tried to point up positive efforts his government was making toward a solution.

"At the point when Congressman Fauntroy was saying, 'If what you're telling us is true, then the press has been presenting a rather amazing image of South Africa,' I had the message from the press waiting outside asking if I knew it was a sit-in and wanting a comment," Fourie recalls. "I said, 'Well, Congressman, I've got something here now that the press says that will really make you laugh.' "

Robinson told him that a sit-in was exactly why he, Fauntroy and Berry were there, Fourie goes on, "And I said 'Well, in those circumstances, there's no use continuing our discussion because I thought it was a serious discussion.' They said they didn't intend to leave and finally we asked [the State Department] that they be removed -- we didn't ask that they be arrested or anything like that."

Police removed the three from the embassy. Arrested and charged with demonstrating within 500 feet of an embassy, a misdemeanor, they spent the night in jail and became the first of 792 to be arrested as of yesterday.

Fourie has told those close to him that he felt he was standing up for all diplomatic missions abroad when he asked that Fauntroy, Robinson and Berry be removed. "He thought that to have someone in the embassy asserting an illegal presence was not a good precedent," says a Washington attorney who sees Fourie often. "The government felt it was an intolerable situation because two people could become 2,000, encouraging even more harmful trespassing."

Fourie scoffs at the notion that the demonstrations have had any significant impact on South African policy. "But what I find new is the strange phenomena with the people who demonstrate. The people who feel so strongly about South Africa are very silent when it comes to Afghanistan, Cambodia and Cuba; one doesn't see any protests from their side. Another aspect I felt puzzled about is there are many countries in Africa where human rights are nonexistent, and they're silent about that."

Fourie believes that the Reagan administration policy of "constructive engagement," the means by which diplomatic channels and not economic sanctions are used to deal with South Africa, "is pretty much alive and, what's more, is proving successful." Others point out that there is no other posture he can take and that President Reagan's call for the improvement of human rights in South Africa had to have surprised Fourie and his government.

Fourie says that he is "in constant dialogue about southern Africa, about our internal situation, and there is a continuing exchange of ideas in a constructive manner" with the Reagan administration. He is said to be a tough negotiator who keeps his feelings to himself.

One friend of Fourie's says that the ambassador was "not so much resentful of the demonstrations as he was disappointed in a situation whereby the South African government was unable to describe the nature of their problem and challenge and what they are trying to do about it . . . Naturally they won't want to say they are influenced by the demonstrations or by what President Reagan is now saying."

Last December, Fourie watched impassively as Nobel Peace Prize winner Bishop Desmond M. Tutu, one of South Africa's leading critics, came to town. Fourie says he made no effort to communicate with him.

"If he came to the embassy I certainly would have received him," says Fourie, though he adds that he would "not necessarily" have entertained him. "If I said I would, he might turn around and say he wouldn't come. So I'm not sticking my neck out unnecessarily."