The 25-year-old has struggled to establish himself as a regular starter at Old Trafford following his 2024 transfer move to the Red Devils.
The Dutch striker has managed just nine goals and four assists across 71 appearances - under multiple managers - who have all failed to get the best out of him in Manchester.
Juventus reached out to his representatives last month over a possible return to Italy, and United are open to a deal, if certain loan conditions are met.
Luciano Spalletti is keen to secure Zirkzee before the new Serie A campaign begins, but Gazzetta dello Sport are reporting a blockage in the ongoing talks, as Juventus do not want a purchase clause included.
United are not rumoured to be pushing for the clause to be mandatory, but they want some assurances over a future sale, as the former Bayern Munich forward is unlikely to force his way back into Michael Carrick's plans.
Zirkzee’s current contract at United is not due to expire until June 2029 and the club hierarchy are determined to ensure they receive a fee whilst his value remains relatively high.
Another stint in Italy could reignite Zirkzee, who enjoyed the best spell of his career at Bologna, scoring 11 Serie A goals in 2023/24, as he helped the club qualify for the UEFA Champions League.