The 25-year-old wants to represent la Roja and the in-form Atletico Madrid striker hopes his decision will not affect his reputation in Brazil
The 25-year-old was granted Spanish citizenship in July and has expressed his desire to play for la Roja ahead of his country of birth should Fifa grant him permission.
"I do not want to create problems with anyone in Brazil," Costa told Marca.
"I want people to accept my decision. Would I have a problem scoring for Spain against Brazil in the World Cup Final? No."
On the topic of a potential call-up for la Roja, Costa says he is far from promised a place in the squad, despite his excellent form for Atletico so far this season.
"Vicente del Bosque has promised me nothing," he continued.
"I know I will have to work very hard to earn a call-up, and hopefully my current form will ensure that.
Finally, the controversial striker admits he doesn't always behave, but puts it down to a tough upbringing in Brazil.
"I have come from having nothing to having everything I want," he said.
"I know what I do on the pitch isn't always right, but I am also provoked more than a lot of players. I came to Spain at a young age, with no friends or family and in a very different culture. It has not been easy."
Costa has scored 10 goals in just eight league games for Diego Simeone's side so far this season.