Rain dampens Australia's hopes of sweeping South Africa off the series

Steady rain threatens to derail Australia's bid of a series clean sweep against South Africa and a confirmed place in the world test championship final as the third and final test against South Africa at Sydney Cricket Ground meanders towards a draw.

After rain delays on both the first two days, further rain Friday meant no play was possible before lunch with Australia unable to add to its imposing first innings score of 475-4 and leaving Usman Khawaja on his overnight score of 195 and tantalizingly close to his first double century.

With more showers expected Friday, Australia has the dilemma of deciding how many runs it needs and then how much time it needs to bowl out South Africa twice on a pitch not yet offering the expected assistance for the spinners.

Australia has already won the series after two crushing defeats in the first two tests at Brisbane and Melbourne.

A win for Australia in this third test would confirm its place in the world test championship final to be played at Lord's in England in June this year.

On Thursday, Khawaja scored his third straight SCG ton and passed his previous highest test score of 174 against New Zealand at Brisbane in 2015 and shared a 209-run partnership with Steve Smith to lift Australia to 475-4 when rain stopped play for the day.

Smith made 104 to join former Australia opening batter Matt Hayden on 30 test centuries. Only Ricky Ponting (41) and Steve Waugh (32) have more among Australian men's test players.

Smith also passed Hayden (8,625 runs) and Michael Clarke (8,643) for career runs and is now the fourth-highest Australian test run scorer with 8,647 runs, behind Ponting (13,378), Allan Border (11,174) and Waugh (10,927).

Matt Renshaw, in his first test since 2018 for the injured Cameron Green, returned a positive test for COVID-19 just before play and was separated from the remainder of his teammates and moved into another changing room at the SCG. He batted as expected at No.6 and was five not out at stumps Thursday.

International Cricket Council regulations state Renshaw is permitted to play in the match as long he feels well enough, with the option for a like-for-like substitute if he was unable to play.