Berlin - World number five Caroline Wozniacki needed nearly three hours to break the resistance of second seed Simona Halep of Romania 7-5 5-7 6-2 on Saturday and reach the Stuttgart Grand Prix final for the second time in five years.
The Dane, a former world number one, will play the winner of the second semi-final later on Saturday between American Madison Brengle and Germany's Angelique Kerber as she eyes her second title of the year.
The first game lasted almost 10 minutes, an indication of the slug match that was to follow on the punishing Stuttgart clay.
Wozniacki clinched the first set after more than an hour when Halep sent a backhand into the net
The world number three, who had 22 unforced errors in the first set, upped her game, racing to a 3-0 lead before being reined in by Wozniacki's thundering groundstrokes.
Halep, who has won three titles this year, levelled but quickly fell two breaks behind again in the third as Wozniacki went 5-1 up.
She saved three match points but could do nothing in the next game as Wozniacki clinched victory after two hours and 58 minutes.