England removed both openers but no one else in the first two sessions, as Australia sought to vindicate stand-in captain Michael Clarke's decision to bat first in the final Test.

Phil Hughes saved the tourists from a rare wicketless session in this winter's Ashes, when he fell to the last ball before lunch at the SCG, and Shane Watson departed with a 50 in his sights during a gloomy afternoon before Australia reached 111 for two at a tea interval brought forward by a rain interruption.

The openers had guided the hosts safely to 55 until Hughes fenced a catch high to third slip Paul Collingwood off the deserving Chris Tremlett.

A second half-century stand followed between Watson and debutant Usman Khawaja, until the former - who had left expertly throughout - followed one from Tim Bresnan that he perhaps need not have, and edged to Andrew Strauss at first slip.

Australia must win here to square the series at 2-2 and therefore prevent Strauss' team becoming the first tourists since 1986/87 to win the Ashes outright down under.

Strauss was unconcerned after losing the toss, reasoning last night's heavy rain and cloud cover presented the possibility of sideways movement.

There was too, for Tremlett in particular, with the new ball.

But after their debilitating 98 all out in the first innings of the fourth Test at Melbourne, Australia were programmed this time to eliminate risk.

So it was that Watson went without a boundary until early afternoon, when he clipped James Anderson off his pads from the 89th ball he faced.

Hughes was slightly more adventurous, but never reckless until his fateful mistake.

The left-hander on-drove Tremlett for four in the fourth over and then had to wait until the introduction of Bresnan, after almost an hour, to count two more boundaries from successive balls - crunched past mid-off and then point, both off the back foot.

It was a measure of England's failure with Plan A - not for lack of effort or accuracy - that Graeme Swann's off-spin entered the attack only 20 overs into the match.

Anderson had been warned by Billy Bowden for running on the pitch in his first spell, and switched first to the Paddington end and then round the wicket too.

But nothing England tried would bring the breakthrough, until Tremlett struck.

Pakistan-born Khawaja, the first Muslim to play for Australia, appeared nerveless as he made an assured start to his innings - tucking his first ball for two off his pads and then crunching a pull for four off the next as Tremlett completed the over interrupted by Hughes' dismissal.

Khawaja's only blemish - before a short break for bad light - was a chancy, aerial cut between the slips and gully for four off Anderson.

Watson clipped Bresnan for a leg-side four to bring up the 50 stand, soon after play resumed under lights, but he was gone two balls later.

A noisy, and mixed, reception greeted Clarke's walk to the crease. He responded with a push through cover for three off Bresnan's first ball, before he and Khawaja closed out the remainder of a session shortened by rain.