Roger Federer broke John Isner just once, but he still claimed a straight-sets win over the American in the US Open fourth round.

The Swiss second seed took just one of his 10 break points, yet still came away a 7-6 (7-0) 7-6 (8-6) 7-5 winner at Arthur Ashe Stadium.

Federer dominated his opening three matches in New York and his shot-making was on show as he advanced without dropping a set.

Isner's serve meant he never found the same rhythm at Flushing Meadows, but he delivered when it mattered against the 13th seed.

Federer made it five wins in six meetings against Isner, who sent down 17 aces and finished with 53 winners.

The 17-time grand slam champion only committed 16 unforced errors to win through a challenging encounter on the back of 55 winners.

Federer will face Frenchman Richard Gasquet in the quarter-finals in a half of the draw that has opened up after Andy Murray's shock loss to Kevin Anderson.

Having looked the more likely to break in the first set, during which he squandered three break points, Federer controlled the tie-break.

The second set was trickier, Federer had to dig out of a 0-40 hole in the fourth game to hold, and the tie-break was also more challenging.

Federer took a mini-break with a fine down-the-line return winner for 7-6 before he crushed a backhand on the line to take the set.

Isner needed to come from 0-40 down to hold in the eighth game of the fourth set, but there was no way back in the 12th.

Federer set up three match points with a backhand winner and victory was secured when Isner put a volley wide.