The South African rand fell on Tuesday as investors pulled out of riskier assets after President Vladimir Putin updated Russia's nuclear doctrine amid escalating tensions with the United States over Ukraine.

At 1056 GMT, the rand traded at 18.0825 against the US dollar, about 0.8% weaker than its previous close. The currency had lost more than 1% against the greenback earlier in the day.

Putin on Tuesday approved an updated nuclear doctrine, with the aim of making potential enemies understand the inevitability of retaliation for an attack on Russia or its allies, driving investors to safe-haven currencies like the dollar.

Traders also said that markets were confident of an interest rate cut by the South African Reserve Bank on Thursday, which could weaken the currency.

South Africa-focussed investors will look to October's inflation print on Wednesday and the central bank's monetary policy decision a day later.

The bank is expected to reduce the repo rate by 25 basis points, according to a Reuters poll of economists, after a cut of the same magnitude at its September meeting.

On the Johannesburg Stock Exchange, the blue-chip Top-40 index was little changed.

South Africa's benchmark 2030 government bond was weaker, with the yield up 1.7 basis points to 9.14%.