The United States Tennis Association (USTA) is going ahead with plans for a U. S. team to play South Africa in the North American Zone final of the Davis Cup at Vanderbilt University in Nashville, Tenn., March 17-19, despite mounting protests that the matches should be canceled or boycotted because of South Africa's repressive racial policies.

"We have agreed to play and we will play." USTA President W. E. (Slew) Hester said yesterday from his home in Jackson, Miss. "We do not support or agree with the apartheid policy of the South African government .... But we have entered the draw and, unfortunately, we have to play South Africa - and in the United States. These areand we are bound by them."

Hester also said he thinks there is a good chance South Africa aill voluntarily withdraw from Davis Cup play in 1979, a course the USTA is urging, and that the South African team coming to Nashville may include a black player for the first time.

Under a new rule sponsored by the USTA and adopted last year by the Davis Cup Nations, governing body of the competition, any country that enters the competition and then defaults for political reasons faces an automatic two-year suspension.

The Coalition for Human Rights in South Africa, an ad hoc group of about 20 organizations, launched what it called a major national campaign yesterday to force the USTA to withdraw its invitation to the South African team.

Franklin H williams, former U. S. ambassador to Ghana and founder of the coalition last fall, said at a Washington press conference that the National Association for the the National Urban League, National Council of Negro Women and other influential civil rights groups comprising the coalition would urge their members toprotest the matches in a variety of ways.

Benjamin L. Hocks, executive director of the NAACP, called for his members to call, write or cable their congressmen, President Carter. Secretary of State Cyrus Vance, the USTA, the mayor of Nashville and the president of Vanderbilt, demanding cancellation of the contest.

Hooks said that if such efforts failed, the NAACP would mobilize the biggest demonstrations this country has seen since the 1960s." He said it had not yet been determined whether such demonstrations would merely voice opposition to South Africa or actually attempt to prevent the matches from taking place.

"If Mr. Hester does not withdraw the invitation. we call on the U. S. Dacis Cup team to boycott the competition," said george Wright, spokesman for the American Committee on Africa, another of the groups in the coalition.

Harold Solomon, Vitas Gerulaitis, Fred McNair IV of Chevy Chase, Sherwood Stewart and Sandy Mayer were named Monday to the U. S. team for the best-of-five-match series.

Some 1,000 picketers protested when the U. S. played South Africa in NewPort Beach, Calif., last April. Play was delayed when demonstrators poured oil onto the court, and U. S. Manager Tony Trabert hit two protestors with a racket when they ran on court during the nationally televised final day matches.

The USTS's position toward South Africa's participation has been widely misunderstood.

"We have never voted specificially for South Africa or anybody else to be included," explained Hester, trying to dispel the misconception that the USTA has supported South Africa in the Davis Cup Nations. "We have ying nation which wishes to play Davis Cup should be included if they abide by the rules, and that any nation refusing to play any other should be kicked out."

Hester met with representatives of the American Coordinating Committee for Equality in Sport and Society (ACCESS) and other active antiapartheid groups last Aug. 17. He promised that the USTA would urge South Africa to withdraw woluntarily in 1979, a prospect he said now appears likely, and would otherwise vote to expel her at the annual meeting of the Davis Cup Nations in July.

Hester also said he has been led to believe that Peter Lamb, a black junior player of international class, would be included on the 1978 South African team.This coalition contends that international team competition is open only to the 20 percent white minority in South Africa, "which makes any claim of a really representative team a mockery."

Others expected to be named are Ray Moore, Byron Bertam, Bernie Mitton, Bob Hewitt and Frew McMillan.

Moore, who says he has remained on the team because it gives him a position of influence from which to speak out against apartheid within South Africa, recently joined Cliff Drysdale a former South African Davis Cupper now living in Texas, in urging South Africa to withdraw voluntarily.

Hester said he was unaware of reports that the Vanderbilt administration was having second thoughts about allowing the matches to take place in its memorial Gym, and that the USTA has made no contingency plans. Dr. Emmett Field, president of Vanderbilt, was unavailble for comment yesterday.