Australia tighten their grip

An unbeaten century from captain Michael Clarke strengthened Australia's grip on the decisive third Test against South Africa in Cape Town.

Clarke was on 161 when the threatening weather finally closed in over Newlands to end the second day's play with Australia on 494-7.

While conditions will leave Clarke with a decision of when to declare, as Australia aim to inflict a first Test series defeat on South Africa in five years, the skipper was able to reflect on arguably the most hard-fought innings of his 104-Test career.

The 32-year-old was left battered and bruised by Morne Morkel on the opening day - prompting him to bat with an arm guard on Sunday - and his path to three figures was hardly easier after a night's rest as he spent 24 balls of the morning session stuck on 99.

Finally, Clarke was allowed a half-volley from Vernon Philander to drive to the cover rope and bring up his 27th Test century from the 215th ball he faced.

That prompted an increase in the scoring rate, although overnight partner Steve Smith had started fluently on his way to 84.

The right-hander most significantly drove Philander and Morkel over their heads for six before being cruelly denied the chance to follow Clarke and David Warner to a century.

Smith aimed to cut at the part-time spin of Dean Elgar but when the ball kept slightly low - on a pitch showing early signs of wear - he managed only to chop onto his middle stump.

At that stage Australia were on the charge and Shane Watson immediately set about increasing the scoring rate as he raced to 40 from 32 balls either side of lunch.

Watson slog-swept JP Duminy (4-73) over square leg only to get carried away and miscue the next ball to Hashim Amla running in from long-off.

Duminy then picked up two wickets in as many balls when Brad Haddin picked out Amla with a fierce drive, before the decision review system detected the faintest of edges behind as Mitchell Johnson tried to turn down leg.

Clarke had already passed 150 for the 10th time in his career and, with Dale Steyn showing no sign of playing any further part in the match after sustaining a hamstring problem on Saturday, South Africa were pleased to see the rain finally blow in over Table Mountain.

That brought a premature end to the day's play with the resumption due to begin half an hour early on Monday, when bright skies are forecast.