Top seed Federer, going for a third successive title at the pre-Wimbledon grass-court tournament, produced a superb display of serve and volley tennis, extending his three-year winning streak on the surface to 28 matches.

Haas, roared on by the crowd in the 12,500-seater Gerry Weber stadium, fought well to take the second set to a tiebreak, but double faulted at 9-10 to hand victory to Federer.

In Sunday's final, Wimbledon champion Federer will play second-seeded Marat Safin of Russia, who beat him on the way to winning the Australian Open this year, or Argentina's Guillermo Canas, the fourth seed.