South Africa's David Bedingham was approaching a maiden Test century as the Proteas extended their lead over New Zealand to 217 at tea on day three of the second Test.

Bedingham had 88 off 108 balls and Keegan Petersen was on 33 as South Africa, needing a win to level the two-match series, reached the interval at 186-4 in Hamilton.

Bedingham and Petersen put on 65 off 19 overs in untroubled fashion following the departure of Zubayr Hamza for 17, caught in the deep when pulling Neil Wagner.

Bedingham, playing his fourth Test, hit 10 fours and two sixes as he unleashed a variety of shots.

The 29-year-old was the only member of South Africa's inexperienced tour squad to play both Tests in the recent 1-1 home series draw against India.

He scored a half-century on debut at Centurion and followed that up with an attractive 87 in the first-Test loss to New Zealand at Mount Maunganui.

Bedingham and Petersen frustrated a New Zealand attack lacking a specialist spinner in conditions which suit slower bowlers.

South Africa took a 31-run first innings lead after dismissing the home side for 211 late on day two but they began their second innings in shaky fashion, slumping to 39-3.

The experiment of opening the batting with wicketkeeper Clyde Fortuin again failed when, after struggling to three off 24 balls, he was trapped leg before wicket by spinner Rachin Ravindra.

New Zealand pace bowler Will O'Rourke continued his eye-catching Test debut with two wickets.

The lively left-armer, who took four wickets in South Africa's first innings, prompted a mis-timed hook from Raynard van Tonder, on one.

South Africa captain and opener Brand had reached 34 when his inside edge off O'Rourke flew to wicketkeeper Tom Blundell.

The under-strength South Africans need a win to deny New Zealand, who won the first Test by 281 runs, a first Test series victory against the Proteas.