JOHANNESBURG (Reuters) -South Africa's rand weakened against the dollar on Wednesday on the view that the U.S. will delay cutting interest rates, with investors on edge ahead of the upcoming elections.

At 1510 GMT, the rand traded at 18.6150 per dollar, around 0.6% below its previous close.

The dollar index rose about 0.1% against a basket of currencies.

"The rand has remained constrained by risk-averse sentiment, with the U.S. stretching out its launch of its anticipated interest rate cut cycle having a negative effect on (emerging markets)," said Annabel Bishop, Investec's chief economist.

Like most emerging market currencies, the rand often takes its cue from global drivers such U.S. monetary policy in addition to local economic data points.

"The expected case rand outlook is also dependent on the outcome of SA's National Election this month," Bishop added.

Polls suggest the ruling African National Congress is likely to lose its majority after 30 years in power when South Africans take to the polls on May 29, with a coalition government a possibility to help the ANC retain power.

But in a note to clients on Wednesday, Citi analyst Luis Costa said the risk premium connected to the upcoming elections had fallen for the local currency, adding that a market-adverse coalition is now seen as less likely.

"With election day premium somewhat past peak, the more fundamental factors in (rand) have been recently supportive of economic activity such as ... the improved domestic load-shedding (which although may not last after the polls close)," Costa said, referring to rolling blackouts.

On the stock market, the Top-40 index closed up around 0.2%, while the broader all-share index had climbed 0.3% from its previous close.

South Africa's benchmark 2030 government bond was weaker, with the yield up 4 basis point to 10.515%.

(Reporting by Bhargav Acharya, Tannur Anders and Rachel Savage; Editing by Christina Fincher and Richard Chang)