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The controversial inclusion of previously suspended US striker Folarin Balogun appeared to galvanise Belgium from the outset, and De Ketelaere poached two first-half goals, in the ninth and 33rd minutes.

The Atalanta forward gave Belgium the lead with a simple tap-in, taking full advantage of a nervous start by the USA to quickly deflate the partisan crowd.

Malik Tillman equalised in the 31st minute with a deflected free-kick, which wrong-footed Thibaut Courtois, but De Ketelaere restored Belgium's lead little more than a minute later with a back-post header, again silencing what had been renewed passion in the stands.

United States played with more authority after the break until a calamitous error from Freese allowed substitute Hans Vanaken to score in the 57th minute, irreversibly shifting the momentum in a stunned Seattle Stadium.

Romelu Lukaku then added a fourth in stoppage-time to send US fans streaming for the exits and Belgium into the quarter-finals for the third time in the past four FIFA World Cups.

It will play European champion Spain in Los Angeles on Saturday (AEST).

The build-up was dominated by US President Donald Trump's unprecedented intervention before Balogun's one-match ban for a red card against Bosnia and Herzegovina was suspended, but the 25-year-old could barely get into the game.

Belgium midfielder Nicolas Raskin said the win felt like a measure of justice after that.

“I think there was always a justice somewhere in life and the fact that something can happen like that, you can put it all you want, but we don't think that was fair,” Raskin said.

“Today, I think it just brings us a little bit of luck. We needed to win the game and the message throughout.”

The US struggled with Belgium's intensity from the start and, with the crowd still going through its first chant of "U-S-A!", Timothy Castagne forced Freese into a fingertip save.

Belgium should have been ahead after a brilliant run from Dodi Lukebakio, impressive in place of Jeremy Doku, produced a great chance for Youri Tielemans, who totally missed his shot.

The co-host did not learn its lesson, though, and a minute later De Ketelaere tapped home Nicolas Raskin's cross after the US failed to clear its lines.

The US looked stunned and was grateful for the hydration break, levelling shortly after the resumption when Balogun won a free-kick in a dangerous position.

Tillman's effort took a wicked deflection off the forehead of Vanaken, an early substitute for the injured Amadou Onana, which gave Courtois no chance.

But the hosts swiftly conceded another cheap goal, with Leandro Trossard standing up a simple cross for De Ketelaere to outmuscle Tim Ream and head home.

United States looked more composed after the break, but any hopes of a comeback were shattered when Freese dawdled on the ball out of his goal and gave Vanaken a shot at an open goal after De Ketelaere had pinched possession.

The game had long since petered out when Lukaku bagged his seventh career FIFA World Cup goal and 93rd for Belgium with a cool finish after US defender Chris Richards found himself isolated on the edge of the box and coughed up possession.

"From the beginning, we didn't connect with the game," United States coach Mauricio Pochettino said.

"Even when we scored the goal, 1-1, we conceded in the next action."

The US's elimination means all three co-hosts are out of the tournament, after Canada and Mexico also lost in the Round of 16.

"In the moments that we were doing well [in the tournament], we felt amazing," US midfielder Tyler Adams said.

"And then obviously, an opportunity like today, we didn't grasp it – and it's gonna sting."