Chelsea striker Romelu Lukaku struck the decisive blow in extra-time as Belgium overcame a spirited USA to set up a mouth-watering date with Lionel Messi's Argentina in the quarter-finals.
Touted as dark horses heading into the World Cup, Belgium have so far ground out results on their first appearance at the tournament since 2002 – but their methods are clearly working.
Only an inspired performance from Everton keeper Tim Howard kept them at bay over 90 minutes but Kevin De Bruyne, rarely used in his brief spell with Chelsea last year, finally breached his goal early on in extra-time.
Soon after substitute Lukaku – who had sparked the attack in which De Bruyne pounced – found the net for his first-ever World Cup goal and it proved a vital one after Julian Green netted a stunning consolation for the USA.
Jurgen Klinsmann's men then came close to an equaliser several times in a breathless encounter.
Lukaku's form had stuttered before his star cameo, as rising star Divock Origi received the nod in the Belgium starting line-up following his own impressive performances from the bench.
And he nearly justified his selection with just 40 seconds on the clock after latching onto a De Bruyne through ball and forcing a fine save from Howard.
That initial excitement quickly died down as defence won out over attack, save for brief glimmers from Belgium.
However the game opened up with a flurry of chances midway through the first half, first former Fulham star Clint Dempsey testing Thibaut Courtois following a slick exchange with Michael Bradley.
Down at the other end De Bruyne – Belgium's top scorer in World Cup qualifying – dragged a glorious chance wide after a fine ball from Tottenham defender Jan Vertonghen.
DaMarcus Beasley was then quick to react to a teasing ball from a lively Vertonghen, with Origi looming just behind.
And the USA could have headed in to half time a goal to the good but Graham Zusi misaimed horribly from substitute DeAndre Yedlin's cross, who had been brought on following an injury to Fabian Johnson.
Howard was called into action immediately after the break, tipping Dries Mertens' slow, looping header over the bar.
Origi then nearly caught Howard out with another header only to see his effort bounce off the bar, and moments later Howard stopped a drilled effort from Vertonghen.
A frantic few minutes ended when Origi, carving out space at the edge of the six-yard box, pulled back for Mertens but the winger's flick missed by inches.
Magical footwork by Kevin Mirallas nearly created an opportunity out of nothing as the final 20 minutes approached, the ball breaking to Origi whose drive was straight at Howard.
And Belgium still went closer when the 19-year-old dissected the American defence to return the favour for Mirallas, but Everton teammate Howard brilliantly saved his goal-bound shot with an outstretched boot.
The Europeans were well and truly in the driving seat as an uncharacteristically quiet Eden Hazard failed to catch out the impressive Howard with a low strike.
Marouane Fellaini, Origi and particularly Mirallas were all exploiting the space in front of a dangerously deep American backline but it was going to take some doing to beat the man between the sticks.
In last-ditch attempts to avoid extra-time, Hazard thrashed into the side netting and skipper Vincent Kompany could not meet De Bruyne's cutback with a true connection.
And in the depths of injury-time USA substitute Chris Wondolowski blazed over from point-blank range, though a wrongly-called offside spared the forward's blushes.
But Belgium nerves disappeared moments into extra-time, as a typically-powerful run from Lukaku saw the ball break to De Bruyne, who twisted and finished low across Howard.
And before the first half was out De Bruyne picked out Lukaku's diagonal run, who lashed home with his left foot.
But fellow substitute Green dragged the Americans right back in it with a sensational over-the-shoulder volley from Bradley's clipped ball.
With their tails up Jermaine Jones spurned a gilt-edged chance to level but hooked wide, while Howard thwarted Lukaku moments later.
Still the USA came and it was time for Courtois to play the hero keeper, bravely saving at the feet of Dempsey after a cleverly-worked free-kick – and ultimately Belgium hung on.
Belgium 2
De Bruyne 92, Lukaku 105
USA 1
Green 107
Referee: Djamel Haimoudi (Algeria)
Attendance: 51, 227
Belgium: (4-2-3-1): Courtois, Alderweireld, Van Buyten, Kompany, Vertonghen, Fellaini, Witsel, Mertens (Mirallas, 60), De Bruyne, Hazard (Chadli, 111), Origi (Lukaku 91)
Subs not used: Mignolet, Vermaelen, Lombaerts, Dembele, Januzaj, Ciman, Bossut
USA: (4-1-4-1): Howard, Johnson (Yedlin, 32), Gonzalez, Besler, Beasley, Cameron, Zusi (Wondolowski, 72), Jones, Bradley, Bedoya (Green, 105), Dempsey
Subs not used: Guzan, Brooks, Johannsson, Diskerud, Davis, Beckerman, Altidore, Chandler, Rimando
