Ireland take on Sweden at the Stade de France in Paris on June 13. Erik Hamren's side head into the clash after soundly beating Wales 3-0 in Solna on Monday and O’Neill is wary of the threat that they, and Ibrahimovic, present.
"[It was] very strong," O’Neill replied when asked what he thought of the performance of Erik Hamren's side against the Welsh.
"[They are a] good side, it will be a difficult game for us but we just have to be ready for it now next Monday.
"Naturally we will have to be very concerned about Ibrahimovic. He’s a top class player, one of the best in Europe and just an exceptional talent.
"We will have to be carefully matched, we will have to watch him and try match up against him but I’m not so sure about someone man marking him."