With just 10 La Liga games remaining, Bilbao hold a six-point lead over fifth-placed Real Sociedad in the final Champions League position.
However, Iturraspe has refused to admit that their place in Europe for next season is secure.
"We know it will be very complicated," he told reporters at a press conference.
"We will work hard until the last day. No one can be in the Champions League every year."
Bilbao finished 12th in La Liga last season.