Wales's bonus point victory over Argentina was good enough to secure second place in their Pool and a last four shoot out against New Zealand.
WRU Audio: U19 Coach Justin Burnell evaluates the prospect of facing New Zealand
Neath and Ospreys wing Leigh Halfpenny helped himself to 14 points, talking his tournament tally to 39 in three games, as the Welsh players turned on the style against the Pumitas.
Having lost their opening game 37-14 to pre-tournament favourites New Zealand, Warburton's side have recovered magnificently to notch successive bonus point wins over Samoa (33-20) and Argentina.
Maesteg outside half Gareth Owen got the ball rolling with Wales's first try, which Halfpenny converted, and Tumble flanker Nick Cudd grabbed try number two before Halfpenny added a penalty to make it 15-nil at the interval.
Halfpenny then extended the lead to 22 points with a try of his own and a conversion. He also converted the bonus-point try from Bedwas wing Jimmy Norris to round off a successful night's work.
Wales last reached the final in 1999 when the tournament was held in Wales, and have yet to win the World title at this age group.
IRB U19 World Championship Semi-Finals
April 17th 2007
17:30 (Semi 1 - 2nd v 3rd) Australia v South Africa - Ravenhill
19:30 (Semi 2 - 1st v 4th) New Zealand v Wales - Ravenhill
Wales: Tries: G Owen, N Cudd, L Halfpenny, J Norris. Cons: L Halfpenny (3). Pen: N Halfpenny
Wales U19 (to face New Zealand):
15. Daniel Evans (Llanelli / Scarlets)
14. Jimmy Norris (Bedwas / Dragons)
13. Luke Ford (Wanderers / Blues)
12. Rhys Williams (UWIC/ Scarlets)
11. Leigh Halfpenny (Neath / Ospreys)
10. Gareth Owen (Maesteg / Ospreys)
9. Gareth Williams (Wanderers / Blues)
1. Ryan Bevington (Bridgend / Ospreys)
2. Huw Dowden (Beddau / Blues)
3. Lloyd Elliott (Ospreys)
4. Haydn Pugh (Llangennech / Scarlets)
5. Josh Turnbull (Llanelli / Scarlets)
6. Jevon Groves (Cardiff / Blues)
7. Nicholas Cudd (Tumble / Scarlets)
8. Sam Warburton (Capt, Wanderers / Blues)
16. Ben Roberts (Ebbw Vale / Dragons)
17. Sam Hobbs (Pontypridd / Blues)
18. Phillip Price (Bridgend Athletic / Ospreys)
19. Nathan White (Bridgend / Ospreys)
20. Lloyd Phillips (Narberth / Scarlets)
21. Jonathan Griffiths (Glynneath / Ospreys)
22. Rhys Webb (Bridgend / Ospreys)
23. David Langdon (Ebbw Vale / Dragons)
24. Tom Williams (Bridgend / Ospreys)
25. Nicholas Harwood (Bonymaen / Ospreys)
26. James Egan (Cardiff / Blues)