Spain cannot select Ansu Fati yet due to a lack of clearance from FIFA, the Under-21 coach Luis de la Fuente has confirmed.
Born in Guinea-Bissau, the forward also had the option to represent Portugal at international level, but has been granted Spanish citizenship and chosen to play for La Roja.
Fati will have to wait for his first taste of international action, however, after he was left out of Spain's senior and Under-21 squads on Friday.
"I waited until the last moment," De la Fuente told a news conference of Fati's absence.
"But it is for the simple reason that he is not selectable. I do not know the details, but he lacks some procedure with FIFA."
Spain senior coach Robert Moreno also said Fati was on his radar ahead of Euro 2020 qualifiers against Norway and Sweden this month.
"I considered calling him," Moreno told reporters. "He was on the pre-list.
"We thought he could do well. He was on the pre-list, we value him, there were a number of events that have been going on, bureaucratic issues after he was injured and we could not summon him.
"Allow me for this exception when talking about someone who is not on the list, but he was a special case that had to be treated in an honest way."
Fati could also be selected for the Under-17 World Cup by Spain, with the tournament set to run from October 26 to November 17 in Brazil.