Vicente del Bosque's men will be looking to become the first team since Brazil in 1962 to successfully defend their world title and the Barca star is confident that La Roja have what it takes to go far at this summer's tournament.
"We'll be on a different stage, it's a different moment but what hasn't changed is our determination to do things well," Iniesta told reporters.
"We've got an extra, additional responsibility this time – we're the defending champions; we'll be going to Brazil hoping to play an important role.
"We've got a great side to be able to do that and, like before, we'll be taking it one step at a time."
Spain meet Netherlands, Chile and Australia in Group B at this summer's finals. Their tournament kicks off against the Dutch on June 13 in Salvador.