Bayern will go to the Nou Camp defending a 4-0 first-leg lead.
But Bartra warned: "It's a little hard, losing 4-0 is not easy, but we must move on. There remains one game, our stadium must be a fortress, everyone should come and support.
"If we did it against Milan, why can we not do it now?
"We are Barça, we are the best team in the world, we were before and we still are."