The Spanish Football Federation have written to FIFA requesting to select the 24-year-old despite the forward having played twice in friendlies for Brazil – the country of his birth - earlier this year.
"I cannot confirm anything yet," Del Bosque told La Sexta. "There is a process to see if he can play for Spain and that process is what is happening now.
"The squad will be called on Friday, we shall see. I know that right now everyone is awaiting news on Diego Costa, but this is a process."
Costa has scored eight goals in La Liga so far this season.