Ivo Karlovic powers into second round

Ivo Karlovic has booked his place in the second round of the US Open with a straight-sets win over Federico Delbonis.

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The big-serving Croatian fired down 21 aces on the way to a 6-3 7-5 7-5 victory over the Argentine.

The 21st seed had as many as eight break-point opportunities during the opening set, but he was only required to take one of them to move into the lead.

Delbonis had chances to break Karlovic in both the second and third sessions, but at the end of each set, he dropped his own serve to allow the veteran to secure his place in the last 64.

The 36-year-old will now face Jiri Vesely on Thursday.