WALES got their World Rugby U20 Championship campaign off to a flying start after edging out hosts Argentina 30-25 in a topsy-turvy clash.

The momentum and the lead changed frequently on the plastic pitch in Rosario yet crucially it was the Welsh youngsters that had their noses in front after 80 hard-fought minutes.

The kicking of Ospreys fly-half Cai Evans, who helped himself to 20 points from the tee, proved to be key as Gareth Williams' side set up a vital Pool A clash with champions France on Saturday.

The weekend clash with Les Bleuets, champions on home soil last year and who beat Wales 32-10 in Vannes on their way to second place in the Six Nations, meant that Gareth Williams' side had little margin for error in their opener against the hosts.

And they got the job done against the livewire Argentineans, just, to ensure they will head into that clash with semi-final hopes.

Three Dragons started the game but centre Aneurin Owen last just two minutes after a nasty clash of heads in midfield.

Thankfully the teenager, who is set to do maths and history A-level exams while out in Argentina, was able to walk from the field unassisted after lengthy treatment.

Wales shrugged off that disappointment to start strongly with the assistance of Argentine indiscipline, Evans earning a 3-0 lead from the tee in the fifth minute.

However, the Pumitas settled and pressure in the Welsh half deservedly led to prop Francisco Minervino finishing from close range after a chip and chase, fly-half Geronimo Prisciantelli converting to make it 7-3.

The hosts' tails were up and Prisciantelli extended the lead to 10-3 from the tee before Wales suffered another blow when a second Dragon, flanker Lennon Greggains, was forced off by injury when clutching his ribs.

Nonetheless, they reduced the deficit to 10-8 with a cracking score in the 28th minute when a grubber through was gathered by Dragons wing Rio Dyer, who offloaded to supporting Ospreys scrum-half Harri Morgan.

Evans' conversion hit the left post but he bisected the posts in the 36th minute to punish a breakdown offence and earn a slender 11-10 lead that they held at the break after Prisciantelli missed a penalty earned with a strong scrum.

The Pumitas got their lead back in the 44th minute when a strong run from a scrum led to a break down the left flank and then, after desperate defence by Dyer, a cross-kick to put Rodrigo Isgro Alastra over.

The winger chose to dive acrobatically over the line rather than go closer to the posts and the kick was missed from the right, meaning it was 15-11 rather than 17-11.

Evans swiftly cut the gap to a point with a sweet strike from the left and had a shot at goal from halfway after an Argentine offside, beautifully knocking it over for a 17-15 advantage.

The hosts weren't quick learners and another offence – not rolling away – not only led to three more points from Evans' boot but a yellow card for Ramiro Tallone Naddaf after 55 minutes.

But the 14 men were ahead on the hour after a magnificent individual score by full-back Ignacio Mendy, who showed pace and superb footwork to go under the posts from halfway, making the conversion a simple one for De La Vega Mendia.

Evans put the restart straight back out and the momentum looked to have shifted back to the Argentineans, only for Scarlets wing Ryan Conbeer to dart through from a ruck after a strong lineout drive.

His fly-half converted to make it 27-22 with 14 minutes remaining and was presented with a simple chance to seemingly make the game safe with 74 gone when Argentina, in their desperation to deny a try inside their 22, were caught offside in front of the posts.

However, Mendia responded in kind to make it 30-25 with three minutes remaining and give hope to the home crowd.

Wales started to get on the wrong side of Scottish official Ben Blain but a knock-on in their 22 at the death sparked wild celebrations in red.

Wales Under-20s: Ioan Davies (Cardiff Blues), Rio Dyer (Dragons), Aneurin Owen (Dragons), Tiaan Thomas-Wheeler (Ospreys), Ryan Conbeer (Scarlets), Cai Evans (Ospreys), Harri Morgan (Ospreys); Kemsley Mathias (Scarlets), Dewi Lake (Ospreys, captain), Ben Warren (Cardiff Blues), Morgan Jones (Scarlets), Jac Price (Scarlets), Lennon Greggains (Dragons), Tommy Reffell (Leicester Tigers), Jac Morgan (Aberavon/Scarlets).

Reserves: Will Griffiths (Dragons), Garin Lloyd (Ospreys), Rhys Davies (Ospreys), Tom Devine (Dragons), Nick English (Bristol Bears), Teddy Williams (Cardiff Blues), Ed Scragg (Dragons), 
Iestyn Rees (Scarlets), Dafydd Buckland (Dragons), Max Llewellyn (Cardiff Blues), Deon Smith (Dragons), Tomi Lewis (Scarlets).

Wales scorers: tries – H Morgan, R Conbeer; conversion – C Evans; penalties – C Evans (6)