A 2% fall in the Dow weighed on the JSE on Tuesday, with the local bourse seeing broad-based losses as markets digested worrying signs about the global economy.

Weak economic data of late has raised concern that the US-China trade war has been damaging, although all eyes this week are on the US Federal Reserve monetary policy decision.

The Fed is widely expected to raise interest rates for the fourth time by 25 basis points, but its forward guidance will be closely watched, due to concern it may press ahead with further tightening, even as the US economy cools down.

A no-confidence vote in the UK parliament against Theresa May is also on traders' radars.

At 9.30am the all share was down 1.85% to 50,065.4 points and the top 40 2.02%. Industrials had lost 2.16%, banks 3.19% and financials 2.48%.

Sasol had slipped 2.96% to R415.94.

Rand hedge AB InBev was down 2.64% to R991.80, Richemont 3.4% to R89.84 and British American Tobacco 1.15% to R475.60.

Sibanye-Stillwater was down 4.86% to R9.79.

Nedbank had given up 4.41% to R253.67, Absa 3.93% to R152.10, Standard Bank 3.04% to R168.35 and FirstRand 3.1% to R62.50.

Shoprite was down 3.95% to R182.75.

Naspers had lost 2.07% to R2,760.

Gold was flat at $1,246.47 an ounce while platinum had fallen 0.4% to $789.83. Brent crude was 0.45% lower at $58.42 a barrel.