John Isner has powered into round two of the Italian Open with a straight-sets victory over Joao Sousa.

There was little to separate the players during a cagey opening set, but it was 16th seed Isner who prevented a tie-break when he broke the Portuguese to clinch it 7-5.

The American held off Sousa to move into a 4-1 lead at the start of the second, and from there he was able to close out the contest 7-5 6-3.

Waiting for Isner in the second round is Leonardo Mayer following the Argentine's win over wildcard Federico Gaio.