The Brazilian is set to play for Vicente del Bosque's side at the next World Cup after impressing with his form for Atletico Madrid
The Brazil-born striker, who initially signed for the Rojiblancos in 2007, has been granted Spanish citizenship, which entitles him to switch to la Roja, having never represented the Selecao at any level.
Coach Vicente Del Bosque recently encouraged the Atleti star to make the switch and, according to the Spanish Football Federation [RFEF] Costa has verbally agreed to link up with the World champions for future internationals.
However, the 24-year-old will not be eligible for selection for the country's upcoming World Cup qualifiers with Belarus and Georgia due to a bureaucracy issue.
The statement read: "Diego Costa wants to play for the Spanish national team, although bureaucracy inhibits this for the moment.
"Atletico Madrid player Diego Costa cannot be selected tomorrow by manager Vicente del Bosque for the upcoming games against Belarus and Georgia as Fifa have demanded additional paperwork, which is already being undertaken, even though the player has verbally expressed to the Spanish coach his desire to play for his national team in the future."