Zola Budd, pursued by anti-apartheid activists since taking British citizenship in 1984, quit world track and returned to her native South Africa today. She said she did not know if she would ever compete again.

The decision by Budd appeared to eliminate two shadows hanging over this summer's Olympics, one involving a threatened boycott and the other the possible barring of the entire British track team.Budd said she was quitting because of "nervous exhaustion." A doctor who treated her over the weekend was quoted as saying that Budd was "a pitiful sight."

Budd, 21, arrived on a flight from London about 2 a.m. (EDT), unescorted except for an airport attendant who helped her with her baggage. She told reporters she planned to stay with her mother in Bloemfontein, south of Johannesburg.

Budd said she would stay in South Africa "until I am healthy again."

Asked whether she intended ever to run again, she replied: "Not at the moment." Concerning a possible return to Britain, her adopted country under whose flag she had hoped to compete in the Olympics in September, she said: "I can't decide about that now. I am very disappointed."

Reaction from the anti-apartheid lobby was quick and strong.

"Her return to South Africa now literally vindicates our position that she is a South African," Sam Ramsamy, head of the South African Non-Racial Olympic Committee, said in London. "It shows she merely used her British passport as a flag of convenience."

Budd said she had nothing to add to a statement released in London Monday night, in which she announced her withdrawal from international athletics to recover from "nervous exhaustion."

In the statement, released to the British news agency Press Association, Budd said she needed a "substantial period of recuperation along with the support of my family and friends to regain my health."

The athlete said she was not well enough to go on battling contentions that she had participated in a sports event in South Africa a year ago in violation of International Amateur Athletics Federation regulations. Budd has denied breaking any rules.

Budd took British citizenship four years ago on the basis on her grandfather being born in Britian. South Africa is banned from international athletics because of its apartheid policies.

The world athletics federation has demanded that Britain bar Budd from international track events for a year because of her appearance at a track meet in Brakpan, near Johannesburg, last June.

Black African nations had warned they could boycott the Seoul Olympics unless Budd was punished. And the IAAF threatened to act against the British board unless Budd was suspended.