Roger Federer has battled through to the third round of the Sony Ericsson Open in Miami, Florida, thanks to a straight-sets win over Ryan Harrison.

The world number three continued to show the resurgent form that won him the Indian Wells title last week as he broke the American twice to take the first set 6-2.

The Swiss kept his opponent at arms length at the start of the second as he found a break of serve early on.

However, Harrison fought back to break his opponent for the first time in the match to take the set to a tie-break.

As both players held serve, it was Federer who snatched a mini-break at 4-2 before he again broke Harrison to win 7-3.