The Roja boss pinpointed matches against Les Bleus and the Scandinavians as his side's most difficult tests en route to the forthcoming showpiece event in Brazil
The reigning world champions currently top Group I with seven points from three matches but recently saw their run of 24 straight victories in pre-tournament campaigns come to an end by virtue of a draw with Les Bleus.
"Spain's fate in the qualifiers will be decided by the games against Finland and France in March," the coach told reporters.
"It is our duty to represent both the Spanish Football Federation (RFEF) and the Spanish people."
Del Bosque also voiced his thoughts on the title race in La Liga, highlighting the increasing competition between Catalan powerhouse Barcelona and both Madrid clubs.
"Barcelona currently hold a substantial lead over Real Madrid and Atletico to a lesser degree," the former Blancos boss added.
"This weekend's match [between Barca and Atleti] will be very decisive."