Johannesburg - The rand extended its decline to reach its lowest level since March 2009 on Friday and is on track for one of its worst falls since the end of apartheid in 1994.
The rand was at R10.0825/$ at 07:49 on Friday, down 0.4% from its close in New York.
It breached the psychologically key level of R10.0/$ on Thursday after a speech by President Jacob Zuma intended to allay concerns about labour unrest disappointed investors.
The last time the rand came close to these levels was in 1998, 2001 and 2008, Rand Merchant Bank analysts wrote in a note published on Friday.
"USD/ZAR started May at R8.97. Assuming we end the month at current levels, the total fall in the rand would be around 13%," the note said. "This would make it the fourth worst fall in the post-apartheid period."
However, the note added that the recent bout of weakness was not yet as severe as the previous blowouts.
If trade data due on Friday disappoints, the rand could come under more pressure given concerns about South Africa's large current account deficit.
South Africa's trade gap narrowed to R7.77bn ($866m) in March from R9.52bn in February.
Government bonds weakened, with the yield on the 2026 issue climbing 10 basis points to 7.5% and that on the 2015 paper gaining 7.5 basis points to 5.54%.