Wales Under-20 reached the International Rugby Board Junior World Championship semi-finals by holding off their Argentine counterparts.
A Hallam Amos try and eight Sam Davies points from the boot gave Wales U20 a 16-0 half-time lead.
Pablo Matera struck back and Patricio Fernandez kicked five points before Davies added a penalty brace.
Santiago Cordero burst clear late on, Fernandez converting, but a late Davies penalty ensured Wales' win.
Danny Wilson's side had beaten Samoa 42-3 and Scotland to set up the clash against Argentina, who had beaten the Scots 44-13 and the Islanders 28-16.
In the Pool C decider, Osprey Davies kicked the game's first points within two minutes and Wales held on to the lead throughout Stade Henri Desgrange, La Roche-sur-Yon in France's Loire region.
Newport Gwent Dragon Amos raced clear as Wales attacked from deep, Davies adding the conversion and a drop-goal to seal a confident opening period by Danny Wilson's side.
But Argentina fought back with open-side Matera going over while Fernandez adding the conversion and penalty.
However, Davies calmed Welsh nerves with two more penalties, the later after scrum-half Rhodri Williams - also of the Scarlets - was brought down by lock Guido Petti Pagadizabal's high tackle.
Pagadizabal was banished to the sin-bin, as was replacement Juan Pablo Aguirre in the dying minutes for Davies's final penalty to end the contest.
Wales will face South Africa in the semi-finals on 18 June, with New Zealand versus England in the other semi.
Wales U20: Hallam Amos (Dragons / Newport); Owen Jenkins (Blues / Pontypridd), Steffan Hughes (Scarlets / Llanelli), Jack Dixon (Dragons), Ashley Evans (Ospreys / Bridgend); Sam Davies (Ospreys / Swansea), Rhodri Williams (Scarlets / Llandovery); Gareth Thomas (Scarlets / Carmarthen Quins), Ethan Lewis (Blues / Cardiff), Nicky Thomas (Ospreys / Swansea), Carwyn Jones (Scarlets / Carmarthen), Rhodri Hughes (Ospreys / Swansea), Sion Bennett (Scarlets / Carmarthen), Ellis Jenkins (capt, Blues / Cardiff), Ieuan Jones (Dragons / Newport).
Replacements: Elliot Dee (Dragons / Bedwas), Thomas Davies (Blues / Cardiff), Dan Suter (Ospreys / Bridgend), Jack Jones (Ospreys / Rovigo), James Benjamin (Dragons / Bedwas), Joshua Davies (Dragons / Bedwas), Jordan Williams (Scarlets / Llanelli), Harri Evans (North Wales / RGC)
Argentina U20: Santiago Cordero, Rodrigo Etchart, Santiago Alvarez, Joaquin Paz, German Schultz, Patricio Fernandez, Felipe Ezcurra (captain): Lucas Noguera Paz, Santiago Iglesias, Matias Diaz, Guido Petti Pagadizabal, Tomas Lavanini, Tomas Lezana, Pablo Matera, Geronimo Mazzoni.
Replacements: Facundo Gigena, Julian Montoya, Tomas Ramirez, Vittorio Rosti, Facundo Isa, Juan Bernardini, Emiliano Boffelli, Juan Pablo Aguirre.