Roger Federer will compete for a 99th career title in Halle, battling past American qualifier Denis Kudla despite another error-strewn performance.

The 36-year-old defending nine-time Halle champion won Saturday’s semi-final, 7-6 (7-1) 7-5.

Federer failed to build on an early break as he let Kudla back into the match but raced through a tiebreaker to claim the first set.

His temper flared in the second set through more careless errors, as seen in the previous rounds, but Kudla’s misfired forehand gifted him the deciding break at 6-5. Federer sealed the match on serve in 86 minutes.

Federer will need to win his 10th crown in a 12th Halle final on Sunday to remain world No.1.

Despite 108 rankings places between Federer and his 25-year-old opponent Kudla, it hasn’t been an easy ride for the Gerry Weber Stadion’s dominant king.

He narrowly avoided defeat in the second round when he was forced to save two match points against Benoit Paire. He had to work for his semi-final berth in two tough sets against Australian Matthew Ebden.

In Sunday’s title decider, Federer will face Spain’s Roberto Bautista Agut or Croatian Borna Coric.