AC Milan's move for Porto striker Mehdi Taremi has stalled.
Milan have offered 15m for Taremi, a fee which satisfies Porto.
However, no agreement has yet been reached due to a disagreement over the method of payment.
Milan would prefer to pay the sum in staggered amounts, which Porto are reluctant to accept.
Waiting in the wings are AC Monza, where they hope to take Mila striker Lorenzo Colombo on-loan once the Taremi deal is settled.