The Brazilian is preparing to finalise the paperwork to confirm his Spanish citizenship, after which point he is expected to receive a call-up.
Costa says that they are just now awaiting confirmation from FIFA about his switch of allegiance.
"I don't get involved. What's most important for me is to keep on working," he told AS.
"It's up to FIFA to make the decision. The decision to play for Spain has already been made.
"Spain has given me everything and if I can play for the national team I will do it as well as I can."
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