The Atletico Madrid man has made his mind up as to whom he wishes to represent at international level in future but said he could not reveal which team yet
The Atletico Madrid striker has been in stunning form this season, firing the Rojiblancos to second in La Liga with 10 goals domestically in 2013-14 and adding two more to his tally in Tuesday's 3-0 win over Austria Vienna.
Costa has already featured for the Selecao in friendly fixtures but is eligible to swap to Spanish nationality, something he has expressed an interest in, and the 25-year-old has admitted that a decision has been made but refused to divulge details.
"My decision has been made," he told reporters in Vienna. "But this is not the right time to make it public.
"People who need to know, already know. I have no doubts about what I will do. But I must wait for the right moment.
"If I could say which, I would have done so long ago."
Vicente del Bosque has expressed his desire to bring Costa on board la Roja's set-up ahead of next summer's World Cup in Brazil, though Luiz Felipe Scolari has been extremely vocal in keeping the ex-Valladolid attacker as a Brazil international.