City go to Germany defending a 2-1 aggregate lead.
"Pep (Guardiola) had some nice words for me at full-time, but we're not done yet. We'll see each other again in eight days' time," said Terzic. "It's halftime and the tie is still open.
"We'll be ready to give it our all to overturn the result and reach the next round. We kept their chances to a minimum and posed a threat ourselves going forward. It was evenly matched so we're disappointed with the result in the end."
Dortmund skipper Marco Reus was upset with the way his side had allowed City to take an advantage to Germany.
"We're annoyed. Conceding a second right before the end was unnecessary. Two seconds of us switching off and they showed their quality. We have to stop the cross coming in. On the whole though, I think we produced a great performance," he said.