Reigning European champions Portugal will take on Iberian neighbours and well-fancied Spain in a mouthwatering Group B clash on just the second day of the World Cup.

The only real heavyweight clash of the group stage will see Cristiano Ronaldo take on several of his La Liga friends and foes on June 15 in Sochi.

Portugal have never reached a World Cup final and are hoping to build on their Euro 2016 triumph in France, while Spain will be desperate to prove their humiliating exit as holders four years ago was only an aberration.

Since the debacle in Brazil which saw a 5-1 humbling by the Netherlands and a 2-0 loss to Chile in the group stage, Spain have rebuilt under Julen Lopetegui following a last-16 loss to Italy in the Euros.

Spain cruised through qualifying for this tournament and will arrive in Russia as one of the favourites to lift the trophy on July 15.

Barcelona great Andres Iniesta, who scored the winner in the 2010 World Cup final, is likely to be playing in his final international tournament after leaving the Camp Nou for Japanese side Vissel Kobe.

It could also be a last World Cup for five-time Ballon d'Or winner Ronaldo as he looks to finally make his mark on football's greatest stage.

The 33-year-old has struggled to produce his glittering best in World Cups, with only three goals from three previous tournaments, against Ghana, North Korea and Iran.

But whatever happens in the opening match, both Spain and Portugal will be expected to ease through a group which also features Morocco and Iran.

Morocco were impressive in qualifying for the first time since 1998 but will struggle to hurt the European teams' defences, while Iran can at best hope for some solid defensive displays under Carlos Queiroz.

Should Spain and Portugal progress, both will be confident against either Russia, Uruguay, Egypt or Saudi Arabia from Group A in the last 16.