Having reached the quarter-finals of the competition, Leverkusen are currently preparing to face Inter Milan on Monday night.
Should they progress past the Italian giants, the Bundesliga outfit face the possibility of playing two further matches.
According to Sky Sports News journalist Kaveh Solhekol, Chelsea will have to wait until the German side are not participating in the tournament to get a deal for Havertz over the line.
While it has been claimed that the playmaker has already agreed personal terms, the Premier League outfit are yet to meet Leverkusen's £90m valuation.
If Leverkusen win the Europa League, resulting in qualification for the Champions League, Leverkusen officials may opt to keep hold of their star man for another 12 months. body check tags ::