The Scottish title-winners on Tuesday secured a 1-0 first-leg victory over their Icelandic opponents away from home in what was new Hoops boss Ronny Deila's first game in charge.
The second leg is next Tuesday, 24 hours before League of Ireland Premier Division champions St Pat's host Polish side Legia in the return leg of their tie, the opening encounter of which finished in a 1-1 draw.
Cliftonville of the Danske Bank Premiership have been drawn to face either Belarus' BATE Borisov or Albanian outfit KS Skenderbeu if they get past Hungarians Debrecen, who they drew 0-0 with at home this week.
Meanwhile, the reward for Welsh Premier League champions The New Saints - if they can bounce back from their 1-0 first-leg loss to Slovan Bratislava in Slovakia and win the tie - will be a clash with either FC Sheriff of Moldova or FK Sutjeska of Montenegro.
Other notable ties in the third qualifying round see Feyenoord take on Besiktas, Grasshoppers play Lille and Standard Liege face Panathinaikos.
The first legs are set to be played on July 29 and 30 with the second legs on August 5 and 6.
Valletta FC (MLT)/Qarabağ FK (AZE) v FC Salzburg (AUT)
Cliftonville FC (NIR)/Debreceni VSC (HUN) v FC BATE Borisov (BLR)/KS Skënderbeu (ALB)
ŠK Slovan Bratislava (SVK)/The New Saints FC (WAL) v FC Sheriff (MDA)/FK Sutjeska (MNE)
Aalborg BK (DEN) v GNK Dinamo Zagreb (CRO)/VMFD Žalgiris (LTU)
Legia Warszawa (POL)/Saint Patrick's Athletic (IRL) v KR Reykjavík (ISL)/Celtic FC (SCO)
FC Dinamo Tbilisi (GEO)/FK Aktobe (KAZ) v Strømsgodset IF (NOR)/FC Steaua Bucureşti (ROU)
HŠK Zrinjski (BIH)/NK Maribor (SVN) v FC Santa Coloma (AND)/ Maccabi Tel-Aviv FC (ISR)
FK Rabotnicki (MKD)/HJK Helsinki (FIN) v APOEL FC (CYP)
AC Sparta Praha (CZE)/FC Levadia Tallinn (EST) v Malmö FF (SWE)/FK Ventspils (LVA)
PFC Ludogorets Razgrad (BUL)/F91 Dudelange (LUX) v FK Partizan (SRB)/HB Tórshavn (FRO)
AEL Limassol FC (CYP) v FC Zenit (RUS)
FC Dnipro Dnipropetrovsk (UKR) v FC København (DEN)
Feyenoord (NED) v Beşiktaş JK (TUR)
Grasshopper Club (SUI) v LOSC Lille (FRA)
R. Standard de Liège (BEL) v Panathinaikos FC (GRE)
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