American fourth seed Jack Sock has outclassed seventh-seeded compatriot Steve Johnson 6-4 6-3 to progress to the Auckland Classic tennis final.

Sock, 24, struggled with his serve despite the calm conditions but still managed to win 77 per cent of first-serve points.

He’ll go on to play Portuguese gun Joao Sousa in Saturday’s final.

Johnson was more lethal on serve but struggled to break the world No.23 and committed too many unforced errors.

He won less than half of all second-serve points and saved just one of four break points.

There was little in the match at first, with the two players holding serve with aplomb until Sock broke at 5-4 to secure the opening set.

With momentum on his side, Sock broke quickly in the second set to pull ahead 3-1, before completing the victory with another break at 5-3.