World number one tennis player Roger Federer of Switzerland is through to the semifinals of the Australian Open in Melbourne after a hard-fought straight-sets victory over Spaniard Tommy Robredo.

Federer, the top seed and defending champion, defeated seventh-seeded Robredo 6-3, 7-6, 7-5 in Tuesday's quarterfinal.

Federer's victory sets up a much-anticipated semifinal showdown with Andy Roddick. The American sixth-seed easily disposed his compatriot, Mardy Fish, in the earlier quarterfinal, 6-2, 6-2, 6-2.

In Tuesday's women's game, unseeded American Serena Williams overcame Israeli 16th-seed Shahar Peer 3-6, 6-2, 8-6 in a thrilling quarterfinal that lasted two hours and 34 minutes.

The 19-year-old Peer was trying to become the first Israeli to reach a Grand Slam singles semifinal, and was serving for the match at 6-5 in the final set. But, Williams broke back and won the next two games to grab the deciding set 8-6.

Williams, a former Australian Open champion, will face 17-year-old Nicole Vaidisova of the Czech Republic in the semifinals. Tenth-seeded Vaidisova beat unseeded fellow Czech Lucie Safarova 6-1, 6-4 in the earlier quarterfinal.

Some information for this report was provided by AFP and Reuters.