Civil servants will have to temper their demands for wage increases with understanding for the recession and the resulting shortfall of billions of rands in revenue collection, government warned on Thursday.

Government will put "its cards on the table" about its shrinking spending power when it starts negotiating with trade unions, spokesperson Themba Maseko told reporters at the fortnightly Cabinet briefing.

"It is tough times which call for tough choices to be made. It is absolutely essential firstly for the leaders of the unions, but secondly for the country as a whole to understand what this recession means for our economy, the constraints that it places on us as a government.

"One of the most immediate consequences of this recession is that there is a decline in tax collections."

He was referring to Finance Minister Pravin Gordhan's announcement that revenue collection was R19-billion lower than expected and that this could increase to R60-billion by year's end.

Maseko said the State could not afford to spend all money at its disposal on wage increases because it would have nothing left for other essential services.

"We still need to buy textbooks for learners, we still need to buy medical supplies, we still need to fix a lot of the things that are broken in our public hospitals, so not all the cash that is available for example in the health budget can actually be brought into the salaries."

In addition, Cabinet was expecting pleas from struggling State-owned enterprises for further cash injections, he said, but declined to name the parastatals.

Maseko said however that "at the same time we are committed to making sure than any offer we put on the table is as reasonable as possible, but also it must be affordable.

"If we can explain that properly and thoroughly to unions we believe that when we put issues on the table, they will be understood."

He said the government was half expecting to enter a "strike season" as poorly remunerated civil servants ask for redress, but hoped they would reconsider before downing tools.

Cabinet called on striking doctors to return to work immediately and teachers who have threatened to follow suit to think about the impact on students, he said.

"It is a historic problem. The issue of low salaries for people working in the public sector is something that has gone on for many decades in this country... We did not move fast enough in addressing issues such as salaries of doctors.

"Our plea is for teachers to give negotiators a chance without resorting to strike action."

Maseko brushed aside suggestions that ministers should accept austerity cuts on their own pay packages or that President Jacob Zuma's decision to create six new ministries at a still unknown cost should be postponed.

"In negotiations with the unions that argument may or may not arise. But we have reconfigured government because we believed that we needed a new structure of government to accelerate delivery of services to all citizens."

He said the cost of enlarging the administration would be known around August 24 when all departments had to submit their budget requirements to the treasury.