At 0700 GMT, the rand was 0.23 percent weaker at 13.1850 per dollar compared with a close of 13.1550 in New York.

Investors are also cautious before meetings of the US Federal Reserve on Wednesday and the Bank of England on Thursday, as they assess the effect of tighter monetary policy after years of cheap money.

Growth in Chinese manufacturing slowed more than expected in July, data on Tuesday showed, as the worsening trade dispute with the United States, bad weather and weaker domestic demand weighed on factory activity.

China, a major source of foreign earnings for commodity exporters like South Africa, is engaged in a tariff war with the United States, which earlier this month imposed tariffs on $34 billion of Chinese imports.

Locally, South Africa publishes unemployment and June trade figures.

Bonds were also weaker, with yield on the benchmark debt due in 2026, adding 0.5 basis points to 8.595 percent.

Stocks opened weaker, with the Johannesburg Stock Exchange's Top-40 index down 0.28 percent to 51,805 points.