Pay raise dispute
Unions are calling for an 8.6 per cent pay hike, twice the current rate of inflation, and a 1,000 rand ($138) monthly housing allowance.
The South African government is offering a seven per cent pay hike and 630 rand for housing.
However, it is likely to raise its offer rather than risk a walk-out that could prompt a prolonged public sector strike reminiscent of a 2007 strike that dented the economy and damaged support for Zuma's predecessor.
Experts predict the ruling African National Congress (ANC), in a long-standing alliance with Cosatu and the South African Communist Party (SACP), will give in to the unions' demands.
Tuesday's strike affected schools and public offices, but essential services such as police and hospitals were running, albeit on reduced staffing.
A mid-grade public sector employee makes on average 8,800 rand a month in salary and benefits, above the national average wage of 6,383 rand, according to government figures.