Johannesburg: Striking South African state workers were voting on Tuesday on an increased wage offer made by the government to try to end a nearly three-week-old strike, the COSATU union federation said.

The government increased its offer to 7.5 per cent from 7 per cent — compared to the union demand for 8.6 — after being ordered back to negotiations by President Jacob Zuma, under growing political pressure over the stoppages.

Analysts said the offer improved prospects for a deal to end a strike that has closed schools, prevented hospital treatment and harmed investor sentiment in Africa's biggest economy.

Teachers' union SADTU said its members were likely to reject the new offer.

"The general view is that the offer is being rejected," SADTU president Thobile Ntola told Reuters. The union claims 250,000 members.

Union officials from a coalition of more than a dozen groups representing about 1.3 million striking state workers said a decision on whether to accept the new offer was likely to come early  on Wednesday.

SADTU is the largest state workers' union in the country's biggest labour federation COSATU and has the power to influence other unions to reject the offer.

The Independent Labour Caucus, a separate labour federation from COSATU, said its more than 200,000 workers appeared to be evenly split on whether to approve the new offer.

"Some of the union leaders have indicated to the workers that this is an offer that can be considered favourably," ILC senior official Chris Klopper said.