Washington, DC, USA, 21 July 2016 | AAP-AP

Bernard Tomic has won through to the third round of the Citi Open in Washington DC, beating Donald Young of the United States in straight sets.

But the news wasn’t so good for fellow Australians James Duckworth and John Millman, who were each beaten in the second round.

Tomic, the No.3 seed, was forced to fight through a first set tiebreak, after dropping serve when up 5-4 in the opening set, before running out a 7-6(4) 6-3 winner.

He sent down 12 aces in the win, and rolled through the second set where he twice broke Young’s serve.

Tomic will face Ivo Karlovic – who he holds a 2-1 winning┬árecord over – in the third round after the towering Croatian recorded a 6-3 7-6(4) win over American Brian Baker.

Meanwhile Duckworth struggled to handle big-serving American John Isner, winning just nine points on return in the 6-3 6-4 loss.

No.1 seed Isner banged down 14 aces in the win, and dropped just three points on his first serve as he closed out the straight sets victory.

He’ll now face Cypriot Marcos Baghdatis in the third round, after Baghdatis breezed past Millman 6-2 6-4.