South Africa's rand firmed a touch on Friday ahead of a decision by S&P Global Ratings which could change the outlook on the country's sub-investment grade rating to negative.

At 1500 GMT the rand was at 14.6650 per dollar compared to an opening level of 14.6900, having rallied below 14.70 in the previous session when the central bank, citing growth risks, kept lending rates unchanged.

Africa's most industrialised economy is ranked sub-investment grade by S&P and Fitch, two of the three main ratings firms, and narrowly dodged a downgrade to junk by Moody's earlier this month when the firm opted to only lower its outlook to negative. S&P said last month at a conference in Johannesburg there was no immediate pressure to change the country's "BB" sovereign rating.

"We expect the agency will deliver a negative outlook on (South Africa's) local currency rating, and quite possibly on its...foreign currency rating too," said Annabel Bishop, chief economist at Investec.

The benchmark JSE Top-40 Index was up 0.5% to 50,484.88 points while the broader All-Share Index rose by 0.14% to 56,618.58 points.