Leverkusen's task at Barca's Nou Camp stadium on Wednesday looks to be mission impossible after they lost their last-16 first leg at home but Kiessling is not giving up hope that they can pull off what would be a stunning upset.
"One can dream, that's allowed," Kiessling told a news conference in the Catalan capital on Tuesday.
"We want to be cheeky and avoid showing too much respect," he added.
The size of Leverkusen's task is underlined by the fact that Barca are unbeaten in 13 home Champions League matches since October 2009, with 11 wins and two draws, while the Germans are without an away victory in a decade.
Barca have conceded just five goals in 13 La Liga games at home this season and let in only two at the Nou Camp in their three group matches in Europe's elite competition, both coming in a 2-2 draw with AC Milan.
"On paper the situation looks clear," Leverkusen coach Robin Dutt told Tuesday's news conference.
"But for us the most important thing is to put on a good performance," he added. "We have nothing to lose but can gain a great deal."
Barca coach Pep Guardiola said it would be a mistake to assume Wednesday's game would be an easy ride for the Spanish, European and world champions.
"People predict that we are bound to win comfortably but that does not happen, and less so in European competition," he said. "Matches against German teams are very tough."
Barca said on Tuesday captain Carles Puyol and midfielder Thiago Alcantara were both unavailable because of injury, the pair joining forward Alexis Sanchez and full-back Eric Abidal on the medical list.
