Federer stays on course for final place in Halle

Federer admitted to a "bumpy" start before finding his form

Roger Federer produced a 10-minute blitz to see off the challenge of Germany's Philipp Kohlschreiber and reach the last four of the Halle Open.

The Swiss won 7-5 6-3 to set up a clash with Philipp Petzschner and said it was down to how he finished the first set and took the upper hand in the second.

"Ten strong minutes led to today's success. It was a bit of a bumpy start but then I found my rhythm," he said.

The other semi-final will be between Lleyton Hewitt and Benjamin Becker.

World number two Federer fired 12 aces as he took just over an hour to see off Kohlschreiber, and now faces another German, Petzschner, for a place in the final.

"That is not going to be easy. Philipp has played really well here," said Federer, who has won this competition five times.

All four quarter-finals at the German tournament featured home players.

Petzschner beat Slovakia's Lukas Lacko 6-4 6-3, while Australian Hewitt, the 2002 Wimbledon champion, beat Andreas Beck 7-6 (7-0) 6-1.

The other quarter-final was an all-German affair, with Benjamin Becker beating compatriot Mischa Zverev 7-6 6-0.