Ireland were the dominant force in the opening half and they led 20-5 with half-time approaching. The Argentinans took advantage of a loss in concentration when Roman Miralles scored a try which was converted by Alfredo Cordone to leave just 8 points separating the sides at the break (20-12).
The Irish saw their interval lead slowly eroded with a Cordone penalty after ten minutes of the restart followed by a 22nd penalty-try that put the Pumitas two points in front.
Ireland however re-acted heoically in adversity and they dictated the closing stages, dominating possession to set up the penalty opportunities for Steenson to win the game.
They went back in front when the Queens University player landed his fifth successful kick in the 65th minute and on the stroke of full time, Steenson landed another penalty to seal the victory.
Team manager David Haslett described his side's performance in the closing quarter as "simply magnificent."
"They played some of the best rugby that I have ever seen an Irish side play," he continued, "They took control of the game in that period and totally dominated the closing stages. It was a great victory for them and they deserve enormous credit for their performance."
In the opening half Ireland looked totally comfortable as they raced into a 21-5 after playing some superbly structured rugby. The late score from Argentina can be put down to some degree perhaps to complacency and that looked looked to have been a grevious error when the Pumitas snatched the lead as the game drifted into the final quarter.
However, this Ireland side showed tremendous courage and self-belief to re-assert themselves and once Steenson had kicked them back into the lead, they never looked likely to cede their advantage against physically bigger opponents who were out on their feet by the time the final whistle sounded.
Next up for Ireland is a game on Saturday against France who were narrow 27-26 victors over Italy today.
Ireland Under 21.
ReplacementsKeith Doyle (UCD) for Fitzpatrick 74 mins., Conor Geoghegan (UCD), Neil McComb (Dundee HSFP), Anthony Kavanagh (Garryowen), Robbie Shaw (Wasps), Michael Glancy (Loughborough Uni), Breiffne O'Donnell (UL Bohemians).