Federer is the two-time defending champion

Roger Federer reached the Swiss Indoors semi-finals with a comfortable 6-2 6-3 win over Italy's Simone Bolelli.

The world number two now faces Spain's Feliciano Lopez, who defeated fourth seed James Blake of the United States 6-4 7-6 (9-7) in Basel.

David Nalbandian beat Germany's Benjamin Becker 7-6 (7-4) 6-4 in the other game to set up a meeting with fellow Argentine Juan Martin del Potro.

Del Potro brushed past Russia's Igor Andreev 6-4 7-5.

Two-time defending champion Federer passed up three match points at 5-2 on Bolelli's serve, but served out a love game including two of his eight aces in the match.

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"I tried to step up the pressure and so far that's worked well."

Nalbandian, who won the 2002 tournament, broke Becker to lead 3-2 in the second set before going on to seal victory.

The 26-year-old second seed now has an opportunity to make up for last week's loss to his Davis Cup team-mate in Paris.

Del Potro, 20, is currently ranked one place behind Nalbandian at ninth in the world rankings but could overtake him if he wins the semi-final.

"Last week I beat him in a great match, and tomorrow I've got to be in good shape if I want to do it again," said Del Potro.

"My mind is good. I want to keep winning but my physique starts to feel tired. My tennis is going numb."