Substitute Mikel Merino scored a dramatic late winner to put Spain in the quarter-finals with a 1-0 victory over Portugal and end Cristiano Ronaldo's World Cup career on Monday.

The European champions will face Belgium on Friday in Los Angeles.

In front of a crowd of 70,649 at the air-conditioned home of the Dallas Cowboys, the Iberian derby that on paper promised to be a thriller failed to deliver.

Extra time looked certain, before Ferran Torres slipped in Merino to settle the contest in the first minute of second half stoppage time.

It meant a sour final World Cup match for the 41-year-old Ronaldo, who looked like he was holding back tears at the end.

Ronaldo, now playing for Al Nassr in Saudi Arabia, confirmed on the eve of the encounter that this would be his last dance on football's biggest stage.

One of the greatest players of all time has refused to say when he will end his international career and was ineffective here.

The neighbours came into the contest both unbeaten, but while Portugal looked as though they failed to get the most out of their talented squad, Spain had not even conceded a goal in the tournament.

For all their pedigree, talent and history, La Roja have only lifted the World Cup once, in 2010, while Portugal's best was third place in 1966.

Amidst the presence of Ronaldo and Spain's 18-year-old Barcelona prodigy Lamine Yamal, the last-16 showdown was touted as a showcase of two extraordinary talents at opposite ends of their careers but did not live up to all the hype.