The Atletico Madrid forward's fitness has been all the rage after he suffered a hamstring injury in early May - an ailment that limited him to just nine minutes in the UEFA Champions League final.
However, Del Bosque said Costa was fit again, and would state his case for selection in the US friendly ahead of their Group B campaign against Australia, Chile and the Netherlands.
"Diego will play tomorrow," Del Bosque said on Friday.
"He had a good training session today, he felt good.
"We want him to play and check how he feels, especially after a while since the last that he played a complete match."
"If we thought that there was a risk for Diego Costa playing tomorrow, we wouldn't use him tomorrow," the 63-year-old said.
"We think that he's fine, his medical situation is done, he's ready so we want him to play."
"We are in our second week of training and we're going to use specially those players who weren't able to be here in the first week," he said.
"We are specifically focused on the World Cup, not in their future," Del Bosque.
"They have their own agents who look after their interests and it's been a fact that several players that were in our league are leaving to other leagues.
"David's situation is not unique."
