Six-time champion Roger Federer will play Alejandro Falla in the final of the Gerry Weber Open after both won their semifinals on Saturday.
Federer fired 10 aces and defeated the fourth-seeded Kei Nishikori 6-3, 7-6 (4).
After a first-round bye, Federer began his Wimbledon preparations by defeating Portugal's Joao Sousa on Thursday then had a walkover in the quarterfinals.
Falla rallied to beat 2011 champion Philipp Kohlschreiber 5-7, 7-6 (5), 6-4 to become the first Colombian to reach the final of a grass-court tournament.
The 69th-ranked Falla saved six of the nine break points he faced before defeating Kohlschreiber in 2 hours, 21 minutes.
Sunday's final against seven-time Wimbledon winner Federer will be Falla's second on tour after he finished runner-up to Ivo Karlovic at Bogota in 2013.
Federer, who made his debut at the tournament 14 years ago, will be playing for his 79th title and his seventh from 12 appearances in Halle.