All Blacks fly half Dan Carter says the drop goal in the second half was off the cuff.

The unexpected Carter drop goal helped keep the All Blacks' Rugby World Cup title hopes alive after they beat South Africa 20‑18 in the semifinal at Twickenham this morning.

Carter also says they needed that drop goal.

Impact player Sonny Bill Williams says it was a nerve wracking last few minutes.

Meanwhile, South African coach Heyneke Meyer says he was not happy with their second half performance.

In the second semifinal, the Wallabies play the Pumas at 3am tomorrow.