Federer topples Tursunov in Miami

Roger Federer remained on course to complete the Miami-Indian Wells Masters Series double for the second consecutive year on Tuesday with victory over Dmitry Tursunov to reach the Nasdaq-100 Open quarter-finals.

Champion at the Pacific Life Open in Indian Wells earlier this month, the Swiss top seed beat the Russian 6-3 6-3 to notch up his 45th straight victory on US soil.

"It's always more difficult to play a guy for the first time," Federer said after securing his 25th victory of the season against just one loss.

In the women's event, Russian 12th seed Svetlana Kuznetsova became the first player to reach the semi-finals with a 6-0 7-6 triumph over Ai Sugiyama of Japan.

Earlier, men's fourth seed Andy Roddick ended the surprise run of Simon Greul, beating the German qualifier 6-3 3-6 6-2.

Greul, ranked 130th in the world, went into the match having knocked out Paradorn Srichaphan, Dominik Hrbaty and Tim Henman.

Roddick, the 2004 champion, has yet to reach a final this season.

Croatian Davis Cup team-mates Mario Ancic and Ivan Ljubicic progressed with the minimum of fuss.

Ancic upset Nikolay Davydenko 7-5 6-4 while Ljubicic swept past Christophe Rochus 6-3 6-1.