Stocks slipped, with Shoprite, which runs South Africa's biggest supermarket chain, pulling the bourse down.
At 1510 GMT the rand was trading at 13.6200 per dollar, little changed from a close of 13.6000 on Tuesday.
Markets expect Fed officials will reinforce their recent dovish stance given a stalemate on global trade, signs of a slowdown in the US economy, and waning business and consumer confidence.
"It will be interesting to see whether the Fed's assessment of US growth has changed, with typical recessionary indicators such as persistent stock losses and widening corporate credit spreads levelling off since December," RMB analyst Nema Ramkhelawan-Bhana said in a note.
"But, fourth-quarter high-frequency data would have been sparse due to the Federal shutdown, creating an added air of uncertainty to the committee's growth outlook. This, combined with softer global data, should continue to justify the Fed's cautious stance, which is positive for risk assets."
A dovish Fed and signs the world's no. 1 economy is slowing, have spurred demand for emerging market assets this month and has seen the rand outperform its peers - bar the Russian rouble.
Investors focus was also on Chinese Vice Premier Liu He's visit to Washington on Wednesday and Thursday for a round of trade negotiations with the United States.
In fixed income, the yield on the benchmark government paper due in 2026 dropped 2 basis point to 8.74 percent.
On the bourse, Shoprite issued a profit warning after market close on Tuesday, prompting its shares to plunge by 14.2 percent on Wednesday and dragging on the stocks of fellow retailers Truworths, Woolworths and The Foschini Group .
The retailers, alongside Spar Group, filled the bottom of the Johannesburg Stock Exchange's Top-40 index .
A series of South African retailers have reported poor performance over the last few months, with the country's consumers reining in spending in a lagging economy.
The blue-chip index overall was down 0.47 percent to 47,972 points and the broader all-share index was also down by 0.47 percent to 54,131 points.