BUENOS AIRES, Argentina — Sergio Aguero is recovering after surgery on his left knee and will start treatment soon, Argentina's football association said on Wednesday amid uncertainty about the player's fitness for this summer's World Cup.

The Manchester City striker suffered from pain in his knee since March 11 and was forced out of action for Argentina in two friendlies at the end of March.

On Tuesday, Aguero underwent surgery in Barcelona and will be sidelined for at least four weeks. Argentina's first game the World Cup in Russia is on June 16 against Iceland.

The AFA said on its Twitter account that Aguero "is recovering correctly after the surgery and tomorrow (Thursday) will begin his treatment."

Earlier, AFA doctor Homero D'Agostino told radio station Radio 10 that Aguero's recovery "should take at least five weeks" and that the striker's condition was "worrisome."

D'Agostino added on sports network TyC Sports that Aguero "is not going to be 100 per cent in shape with so little time prior to the World Cup."

Aguero scored 30 goals for Manchester City this season and is considered Argentina's second most important player, behind Lionel Messi.