Milan's general manager Adriano Galliani confirmed to shareholders at a meeting on Friday, when the takeover was due to go through, that there were still complications regarding the sale of the club.
Current owner Silvio Berlusconi agreed to sell the club to the firm last August and has since accepted £170m in non-refundable deposits as they attempt to get the required funding together.
The consortium were unable to meet the latest sale deadline of March 3 and are now thought to have agreed to pay another non-refundable deposit of £85m in order to extend the deadline until March 31.
Galliani says that Berlusconi's company Fininvest "is evaluating the possibility of drawing up an agreement to give up its ownership of AC Milan soon."
"I cannot say at what stage we are and what the future of AC Milan is. Milan do not feel like they are being taken for a ride. Fininvest (Milan's current owners) are fulfilling their duties. They are seeking an agreement with SES as soon as possible", he said.
The £622m deal is thought to be the biggest ever Chinese investment in a European club and includes its £185m of debt.
Former Italian prime minister Berlusconi, who will keep the club and pocket £255m if the deal ultimately falls through, has been in control at San Siro since 1986.