Aberdeen will face FC Kairat Almaty of Kazakhstan or Alashkert FC of Armenia if they complete the job against Rijeka next Thursday.
Ties will be played on July 30th and 6 August 6th.
Kairat hold the upper hand after the second round first leg, with an identical 3-0 lead over their opponents to Aberdeen.
If the Dons win through, they will still have one more round to play bfore the group stages; the Playoff Round, which is contested on August 20th and 27th.
If the Dons clear those hurdles they would reach the group stage of European competition for the first time since the 2007/08 season when Jimmy Calderwood’s side progressed to the last 32 of the UEFA Cup.