American Jack Sock has won the Auckland Classic title with a 6-3 5-7 6-3 victory over Joao Sousa in the tournament decider on Saturday.

There was little in the match between fourth seed and his Portuguese opponent, with momentum swinging throughout the one hour and 56 minute clash.

But after failing to capitalise on chances to secure the match in the second set, Sock dug deep in the decider to peg Sousa back from a break down.

Service was a key plank in both players’ games, with Sock hitting 13 aces and Sousa notching 10.

But it was ultimately the Nebraskan’s potency with his first serve that secured him victory, winning 80 per cent of first-serve points to Sousa’s 67 per cent.

Both players looked on an even keel early on, dictating their service games and forcing their opponent from side to side at the baseline.

Holding their first three games each, it was the Sock who eventually made the breakthrough, capitalising on a failed Sousa drop shot to break serve.

After a brief lapse of two unforced errors at 4-3, he then went on to hold serve and break a rattled Sousa again to win the first set 6-3.

While both finalists looked assured with their first serve, it was the second serve where Sock stamped his authority on the first set.

The Kansas-based player secured an impressive 67 per cent of all second-serve points, while the Barcelona-based Sousa could only win a third.

Sock initially looked likely to romp through the second set, holding serve easily before racing out to a 30-0 lead facing serve at 1-0.

Yet Sousa put up a resistance, rallying to hold serve with four straight points before breaking a careless Sock to lead the set 2-1.

Sock immediately broke back, putting the set on a knife-edge until Sousa pulled a rabbit out of the hat with several beautiful forehands at 5-5 to break serve.

Confidently serving the match into a decider, Sousa looked primed for victory when he quickly broke serve at 1-1 on the back of several Sock unforced errors.

But this time it was the world No.23’s turn to fight back, immediately breaking back and dominating Sousa’s second serve with three thumping forehands down the line.

Serving for the match at 30-30, Sock dug deep to produce two bullet serves that Sousa was unable to handle.

It’s his second ATP title in six finals and his first in Auckland, having pulled out of last year’s Classic final with the flu.