The 25-year-old was one of Bilbao's standout performers in the 2013-14 season, with the defensive midfielder helping his side into fourth place in La Liga.
His form gained him a call into La Roja's squad and the chance to represent the European and world champions in Brazil next month.
"I'd just got out of the shower and the phone started ringing... After that, I had thousands of calls and messages and it truly is a huge joy to be here," Inside Spanish Football quotes Iturraspe as saying.
"Of course I know it's very difficult to get here and into this squad, because there's so many really good players, but we've been having a really good season at Athletic Club Bilbao, so there was always a little hope I could make it."
Del Bosque will name his final 23-man squad over the next week.