Juan Martin del Potro reached his 30th career ATP final as he wore down David Ferrer to prevail at the Auckland Open.

The 2009 US Open champion was faced with an unsurprising show of endurance from his Spanish opponent, who was typically dogged in a contest that lasted one hour and 47 minutes.

But it was Del Potro who was the more clinical in taking his chances, coming through to claim a 6-4 6-4 triumph that sets up a showpiece with another Spaniard, Roberto Bautista Agut.

Del Potro struck in the first game to break but was forced to repeat the feat in the seventh game after Ferrer had levelled matters at 3-3.

That was to be the last blip of the match for the Argentine, though, as he comfortably served out the first set and required just a single break in the second, saving five break points en route to victory.

Speaking on court afterwards, Del Potro, who won the title in Auckland in 2009, said: "I'm exhausted, I'm so glad to be in the final after 10 [nine] years. 

"I tried to serve hard to hit hard with my forehand, to play some slices and drop shots, it's never easy against David because he runs a lot and he's a fighter.

"It's amazing to me just to be playing tennis against after all my wrist problems. If I play well maybe I have a little chance."

Bautista Agut, meanwhile, beat Robin Haase in three sets, all of which went to tie-breaks in a near three-hour slugfest.

The world number 21 emerged victorious 6-7 (7-9) 7-6 (7-3) 7-6 (7-5), with his win sealed in magnificent fashion as Bautista Agut somehow landed an audacious backhand lob inside the baseline.

"When I saw the ball in, I went crazy," Bautista Agut said. "I'm so happy that I won... It was an unbelievable battle on the court."