The Health and Other Service Personnel Union (HOSPERSA) accused the powerful COSATU labour federation, which is spearheading the three-week protest, of pursuing a political agenda in the strike over pay.

"We believe that the offer that the government has put on the table is a fantastic offer for us but we also believe that the strike is now pursuing a political agenda," HOSPERSA President Gavin Moultrie told Reuters.

"What was a mature wage dispute weeks ago has now been turned into a political game by the leadership of COSATU and SADTU and we won't be a part of that ... they are being greedy and opportunistic," he said, referring to the South African Democratic Teacher's Union.

Hundreds of thousands of workers have taken part in the strike that has highlighted deep divisions in the alliance between the ruling African National Congress (ANC) and its powerful trade union allies.

Unions, which collectively represent about 60 percent of the country's nearly one million public servants, accuse President Thabo Mbeki of promoting big business and leaving behind millions of poor South Africans.

HOSPERSA and the National Professional Teachers' Union (NAPTOSA) said their combined total of 160 000 workers would go back to work as other unions consulted their members before talks with the government aimed at ending the dispute resume on Wednesday.

NAPTOSA president Dave Balt told Reuters the union had pulled out of the strike, which has crippled mostly hospitals and schools.

Labour is demanding a 9 percent pay rise. The government, which fears a dramatic wage hike would crowd out other spending, has tabled a final proposal of 7,5 percent and said unions could take it or leave it.

South Africa's central bank has warned a large wage increase would further fuel inflation and raise the prospect of more interest rate hikes.

Economists say it is difficult to count the lost productivity in Africa's biggest economy, but some estimate it may be as high as 3 billion rand.