World number two Roger Federer edged past Ivo Karlovic 7-6(3) 7-6(4) on Saturday to reach the Halle Open final and stay on course for his eighth title in the grasscourt Wimbledon warmup event.
The Swiss top seed, who will meet either Italy's Andreas Seppi or second-seed Kei Nishikori in Sunday's final, held serve throughout but was taken to two tiebreaks having failed to secure a single break point against the Croatian's powerful serve.
It was always going to be a slugfest with Karlovic having fired a record 45 aces past Tomas Berdych on Friday.
The Croat did not disappoint, racking up 10 aces halfway through the first set.
A sensational backhand return in the opening tiebreak gave Federer the slight edge he needed on his opponent's serve and a double fault from the Croatian handed him the first set.
The Swiss again had to stay patient, but won two points on the Croatian's serve in the second tiebreak and sealed his win with a backhand volley after one hour and 28 minutes.
