According to Gazzetta dello Sport (h/t Football Italia), Inter will not sell the player for any price less than their €50 million valuation; if they don't receive an offer that amounts to that sum by July 1, the report added that they won't sell the winger at all.
If Perisic is to stay, Inter are said to have made it clear they will seek to extend his contract beyond its current 2020 expiry.
It's reported Inter are ready to increase Perisic's salary by €500,000 annually and extend his current terms by two years.
United are only ready to offer around €30 million for the 28-year-old, the amount Inter need to ensure they fulfil Financial Fair Play regulations.
Perisic enjoyed a brilliant campaign in an inconsistent Inter team in the 2016-17 season, excelling on the left flank. His purposeful running, clever dribbling and impact in the final third made him one of the most threatening attackers in Serie A.
Per OptaPaolo, the player enjoyed his best goalscoring season in Italy:
While he can be a little inconsistent at times, it's easy to see why United boss Jose Mourinho would want to add Perisic to his squad.
Although players like Anthony Martial, Juan Mata and Henrikh Mkhitaryan add flair on the flanks, they aren't as industrious or as aggressive as Perisic. The Inter man is strong, tricky and relentless in the way he attacks the full-back; he's a player who looks to be tailor-made for the combative nature of English football.
ESPN FC's David Amoyal believes Perisic is the perfect stylistic fit for the Manchester United boss:
United may have felt as though they were able to pressure Inter into selling Perisic earlier in the window, although the Nerazzurri look poised to hold firm on their valuation.
At 28 and on the back of the best season of his career so far, Perisic may feel this summer is an ideal chance for him to make the step up to a club like United. But with three years left on his contract, and Inter in no hurry to cash in, the onus will be on the Premier League side to make this one happen.