JOHANNESBURG, June 12 — A nationwide strike by South Africa’s public-service unions lumbered into its 12th day on Tuesday, shuttering schools, crippling hospitals and hamstringing courts — but not moving President Thabo Mbeki’s government far toward a settlement.
The standoff mirrors South Africa’s political situation, which pits a stoic Mr. Mbeki against left-leaning unions that accuse him of betraying the nation’s vast lower class. The two forces will clash later this year when the dominant political party, the African National Congress, convenes to choose a new president, an act tantamount to selecting South Africa’s next ruler.
The strike so far has inconvenienced millions of South African adults and children girding for midyear exams, but has done little lasting damage. That could change on Wednesday, however, when hundreds of thousands of municipal workers may desert their jobs in sympathy with the strikers.
“They have the responsibility for picking up trash, for keeping the city power going,” said Duncan Innes, an independent labor analyst in Johannesburg. “If they go out, it could be quite disruptive.”
The strike was called by the Congress of South African Trade Unions, or Cosatu, an amalgam of 1.8 million workers, most employed by national, provincial or local governments. The group’s unions had demanded a 12 percent salary increase and other benefits, but lowered their wage demand to a 10 percent increase.
During the talks, the government raised its initial offer of a 6 percent increase to 6.5 percent, although it was expected to make a new offer when negotiations resumed late Wednesday.
The walkout, which the union says includes 700,000 of its members, has been confined largely to teachers, hospital workers and some government functionaries like court orderlies and stenographers. Public schools have been shut since the strike began, and some private schools began closing this week as strikers threatened to picket them. The government has fired thousands of striking nurses, arguing that they violated a constitutional ban on strikes by essential workers, and has deployed army medical workers in public hospitals.
Violence has been limited. But Mr. Mbeki was angered Monday when the general secretary of Cosatu, Zwelinzima Vavi, warned that very soon the strike would turn violent.
Patrick Craven, the spokesman for Cosatu, said in an interview that “the unions are absolutely committed to keeping this strike peaceful, legal and disciplined.” But Mr. Mbeki condemned what he called the unions’ “message of selfish own interest,” and some political and labor analysts said that more violence could erupt if the strike spread to municipal workers.
Nobody disputes that the teachers and nurses who have walked out deserve a raise. A beginning teacher earns about $700 a month, and nurses may earn as little as $500, at a time when food costs are rising 8.6 percent a year.
In some ways, the wage dispute has been overshadowed by the test of political wills between Mr. Mbeki and the unions — a prelude, some say, to the contest for leadership of the African National Congress.
Mr. Mbeki, president of both South Africa and the congress, is legally barred from running again for national president in 2009, but is widely expected to seek a new term as president of the party late this year. The president of the party effectively controls who becomes its nominee for president of South Africa.
Cosatu, which is formally allied with the African National Congress, has remained officially impartial in the leadership struggle. But unofficially, the group has vigorously backed Mr. Mbeki’s populist rival, Jacob Zuma.
Experts say the strike could become more serious if it spreads beyond public workers to private industries vital to the national economy. But, so far, that seems unlikely; the major union representing miners, for example, said this week that it would not join the walkout.
For now, at least, that leaves members of the public sector, whose ability to bring South Africa to a standstill appears limited.