Finance Minister Tito Mboweni has conceded that he is concerned about signs that Moody's will not keep South Africa's investment grade credit rating steady when it issues an assessment on Friday.

"Fitch is really not impressed with us and said, you guys didn't go far enough. Moody's said they will release their review tomorrow and were looking very carefully at our fiscal stance. Let's see what they say, but I really hope they keep the rating the same," he said on Thursday as he briefed a joint sitting of Parliament's standing and select committees on finance and its select committee on appropriations.

"But it is not looking good," he added.

Mboweni was speaking a day after he tabled his medium term budget policy statement. It slashed the growth forecast for the year to 0.5% of GDP and cautioned that the debt to GDP ratio would by 2022/23 exceed 70 if left unchecked.

The finance minister was criticised for not outlining measures to restructure Eskom's debt, which is seen as the biggest risk to the economy.

Moody's is the last of the big international ratings agencies to have kept South Africa's sovereign credit at investment grade. There have been suggestions that it might hold off on an outright downgrade, but move the outlook to "negative". This would signal that the next assessment is likely to see a downgrade.

S&P Global and Fitch have already downgraded the country’s sovereign credit to sub-investment grade, colloquially known as “junk” status.

Mboweni on Thursday said there would no consideration of debt relief for Eskom until the embattled power utility had shown commitment and progress in implementing the unbundling blueprint released by Public Enterprises Minister Pravin Gordhan this week.

He also cautioned that in future financial support for public entities would come in the form of loans.

Mboweni on Thursday repeated his warning that the country was heading for a debt trap and that the answer, for now, was cutting spending and selling off non-performing assets.

He issued a stark rebuke to critics who said debt was not so much the issue but the composition of the country's debt.

"Of course debt matters because it is the first charge on the country's fiscus," he said, adding that it meant less funding for health, education and other services.

"If you are not a reserve currency country you cannot afford these high levels of debt."