South Africa's rand hit a three-week low on Wednesday as the US currency strengthened and the deputy central bank governor warned domestic economic growth continued to disappoint. At 1520 GMT the rand was trading 0.75 percent weaker at 11.8500 to the dollar, its weakest level since February 12. Deputy Central Bank Governor Francois Groepe said on Wednesday economic growth was disappointing, but the bar for South Africa to ease monetary policy remained high, with underlying inflationary pressures persisting.