WASHINGTON, April 1 (Xinhua) -- World number one Roger Federer overcame unseeded Jose Acasuso 7-6(5), 6-2 in the fourth round of a Masters Series tournament in Miami on Tuesday.

The Swiss top seed, who won the title in 2005 and 2006, made it through to his sixth Miami quarter-final on the back of his impressive service game against the Argentine world number 45.

The 26-year-old reached the fourth round here last year, but was upset by Guillermo Canas.

Federer, who lost only 10 points on serve, will meet a familiar rival in Andy Roddick next.

"It was key for me to serve well, especially in the beginning, and it was a good serving day today," said Federer. "I was very happy with it."

Second seed Rafael Nadal, who lost to Federer in the 2005 final,also reached the quarter-finals on Tuesday by beating 15th-seeded Frenchman Paul-Henri Mathieu 6-4, 6-4.

Ninth-seeded American James Blake is through to the quarter-finals after claiming a 6-3, 6-4 win over No. 27 Radek Stepanek.