More states and cities cut their financial ties to South Africa

US human rights advocates are ever-so-slowly tightening the purse strings on American investment in South Africa. The method they have chosen is to force officers of pension funds, public university endowments, and state and local government bank accounts to sell their investments in South Africa, the only country in the world that legally mandates racial segregation, or apartheid.

Two state laws enacted within the past two weeks have given new impetus to the divestiture movement in the United States. In Michigan, the state colleges and universities are now required to withdraw their investments in South Africa. In Massachusetts, the state employees and teachers pension funds must bring home investments in that country, about $100 million, over the next three years. The measure toughens a 1979 law prohibiting new investments in South Africa.

Last summer, Philadelphia removed its pension funds from firms with investments in South Africa or neighboring Namibia, which the white South African government controls despite protests from the United Nations. In June, Connecticut put tougher restrictions on its investments. In all, campaigns to divest have been waged in 17 states and 14 cities, with more expected as legislative sessions begin, says Gail Hovey, who tracks the nationwide divestiture movement for the American Committee on Africa, an anti-apartheid group.

Such actions still run counter to the trend of investments by US corporations , which have grown steadily in recent years. Spurred by a less-antagonistic Reagan administration, total US investment in South Africa rose to $2.63 billion in 1981, up from $2.35 billion in 1980, according to the US Commerce Department.

Whether divestment efforts in the US can - or should - influence internal policies in a sovereign nation half a world away is the subject of heated debate.

William Johnston, president of the New York City-based Episcopal Churchmen for South Africa, argues such legislation ''is the best tool . . . to respond to the horrors of South Africa. It makes US corporations very uneasy to want to stay there.''

''Nothing is happening inside South Africa that's leading toward a more just society,'' he says. Americans ''have to face this situation square on until they have some kind of an equitable society there.''

But US companies operating in South Africa argue they can do more good by staying put than leaving. Many have signed the so-called Sullivan principles, a pledge to provide racial equality at the workplace and take other steps to improve conditions for nonwhites.

Groups pushing divestment laws say the Sullivan principles are only a charade. ''They don't address the fundamental problem of apartheid,'' says Ms. Hovey. She points out that Mobil Oil Corporation, which signed the principles, supplies oil to police groups that suppress nonwhites and to South African military forces occupying neighboring Namibia.

And despite the Sullivan principles, ''If a black man was made the head of Ford Motor Corporation in South Africa, he'd still need a passport to get to work,'' adds Robert Schafer, an aide to state Sen. Jack Backman, who cosponsored the Massachusetts law.

Mr. Schafer says that one key to passing the Massachusetts measure was a study produced by proponents showing that divesting would not harm the pension funds. In fact, the study showed alternative investments could yield a net gain. Deputy State Treasurer Patrick Sullivan later estimated immediate divestment would reduce the $1.5 billion in the funds by about $6.2 million. But careful selling over the three-year period might cut or eliminate this loss, he said. A divestment by Michigan State University several years ago has made money for that fund, advocates say.

The Massachusetts law requires that the withdrawn funds be invested within the state, if fiscally prudent. This may be an attractive feature to other states, says Margaret Ward, who is coordinating the effort to pass divestment legislation in Minnesota. ''It's very significant not only because it is so strong, but because it speaks to the needs of a state to invest at home'' and support its own industries, she says.

Meanwhile, South Africa is mired in a major economic slump of its own. The international market for its exports such as gold, diamonds, and uranium has been soft. And the widening of the Suez Canal has cut the need for supertankers to pass around South Africa's Cape of Good Hope.

If more US companies begin backing out of the country, it is likely to be the result of economic conditions there rather than pressures by US groups, argues Dr. Ragaei El Mallakh, an economist who heads the Africa and Middle East Studies program at the University of Colorado. Although he says the US is moving from support of Pretoria to a ''more objective'' policy under Secretary of State George P. Shultz, ''I don't think a few pension funds [divesting] here and there really make that much difference.''