Lithuanian champions Kaunas were handed a favourable draw in the first qualifying round, after being drawn to face Montenegrin side FK Zeta.
The winners of that tie will go on to face Rangers in a two-legged second-round tie, the matches to be played on July 31/August 1 and August 7/8.
That tie will determine who goes forward to the third and final round of qualifying, the stage at which Scottish champions Celtic begin their campaign.
Kaunas are sponsored by Hearts majority shareholder Vladimir Romanov's bank, Ukio Bankas, and players from the Lithuanian side have been regularly sent to play in Scotland.
Irish Premier League champions Linfield have been drawn against Swedish side Elfsborg in the first qualifying round.
Welsh Premier League winners The New Saints - formerly known as TNS - will face Latvian champions Ventspils, while Derry City will face Armenian Premier League side Pyunik.
The ties will be played over two legs on July 17/18 and 24/25.
In the second round, Derry would face a tricky clash with Ukrainian side Shakhtar Donetsk if they make it through and a game with Hungarian side Debrecen would await Linfield should they defeat their first-round opponents.