The New Zealand forward netted goal number seven for the season with a looping header just before half-time and then pounced to fire number eight past Clint Bolton in the second period.

Sydney fought back with substitute Steve Corica heading one back to set up a tense finish at Skilled Park.

But Miron Bleiberg's men held on to regain top spot and leave Sydney tasting their first defeat.

Much of the pre-match build-up centred around who would assume Jason Culina's role in the mid-field. Gold Coast coach Bleiberg employed Robson, Zenon Caravella and Tahj Minniecon in a rotating three-pronged attack.

Caravella and Minniecon were impressive on the flanks, while Robson kept plugging away through the middle as the home side grabbed the ascendency.

The only negatives for United were injuries to Joel Porter (calf) and Matt Osman (hip) who had to be replaced.

Smeltz's first goal came on the end of a brilliant curling ball from Osman who found his striker to bury the ball into the net with a looping header over Clint Bolton.

The Kiwi striker got his second after some untidy work from Karol Kisel handed him the ball in good position, Smeltz rounded Shannon Cole and fired past Bolton who had little chance.

Sydney had the first real scoring chance of the match when Cole was awarded an early free-kick but he drove his shot straight into a wall of United defenders.

The hosts then went on the attack but failed to convert on at least half a dozen good scoring opportunities before getting their goal in the 45th minute.

First, Minniecon showed sharp skills to put himself into space before crossing for Caravella whose shot sailed just wide.

Caravella had his second near miss when his 30-metre left-footer beat Bolton but struck the left upright to give Sydney a reprieve.

Sung-Hwan Byun drove a shot just wide of the post from a tough position, but Sydney should have been first to score after some neat work from Alex Brosque.

Brosque chipped for Aloisi, ran into space and then received a nice ball back from his skipper to be one on one with Coast 'keeper Scott Higgins but failed to finish.