Australia’s share market finished flat as global investors traded cautiously ahead of a big risk event for financial markets – the first US presidential debate between Donald Trump and Joe Biden.

The S&P/ASX200 benchmark index reached a session high of 5995.4 in the first hour, but then mostly fell away to finish lower by 0.2 points, or 0 per cent, to 5952.1 points on Tuesday.

The All Ordinaries index closed higher by 6.6 points, or 0.11 per cent, to 6141.5.

Mr Trump and Mr Biden will debate how they would help the US economy recover from the coronavirus recession, among other issues, on Wednesday morning (AEST). The election is on November 3.

The Australian dollar was buying 70.81 US cents at 1621 AEST, up from 70.53 US cents after the close of trade on Monday.