Gianluigi Donnarumma
Milan will say they are ready to meet Donnarumma's demands but cannot wait around all summer. Getty

Milan remain hopeful of tying down Manchester United target Gianluigi Donnarumma to a new deal but admit they cannot wait all summer for a decision to be met.

Donnarumma, 18, has a contract at the San Siro until 2018 but has so far failed to reach an agreement with his club over an extension. His agent Mino Raiola, who also represents Manchester United trio Paul Pogba, Zlatan Ibrahimovic and Henrikh Mkhitaryan, remains in talks with the Serie A giants but recently insisted there is "a lot of time" left for an agreement to be met.

Milan insist they are ready to meet any demands made by Donnarumma, who is widely regarded as the best young goalkeeper in football. However, contrary to Raiola's recent comments, the club's general manager Marco Fassone insists the Rossoneri do not have time to wait around for a lengthy contract stand-off and have no option but to draw up a "back-up plan" should no decision be met soon.

"Donnarumma is a cornerstone, a pillar, a foundation for next season, we told him this the first time we met for talks," Fassone told Mediaset. "I can see a willingness to stay in his eyes, but we cannot afford to sit back and wait for him to make a decision. We need to give [Milan head coach] Vincenzo Montella his squad for next season on 3 July. Our time is more pressing than Mino Raiola's.

"We need to know if we still have a goalkeeper, whether he will leave or whether we will have a goalkeeper with an expiring contract. No club would leave a goalkeeper like Donnarumma in the stands, but we cannot have a goalkeeper with an expiring contract.

"I am convinced that our offer and our plans with him are good, but we will have to active a back-up plan if he does not want to renew."

Donnarumma has been touted as a long-term replacement for David de Gea at United, with the Spaniard still being linked with a return to Spain to join Real Madrid.

The Mirror report United will consider a move for the 18-year-old in the event of the Spain international leaving, with Atletico Madrid's Jan Oblak also on Jose Mourinho's shortlist.