The Daily Mail says the Serbian Football Association have written to FIFA as they explore the possibility of recruiting Krkic to play for their national team.
Krkic was born in Spain and grew up in Catalonia. He played for the Spanish youth age groups at Under 17 and Under 21 levels.
He also made one appearance for the senior team under Vicente Del Bosque at the age of only 18 in 2008, when he came on a substitute in a World Cup Qualifying clash against Armenia.
However, Krkic has a Serbian father and therefore could be eligible to change nationality.