The Berlusconi family's Fininvest holding company, which owns AC Milan, started exclusive talks with the Chinese consortium at the beginning of May to try to inject new capital into a club which has failed to win a major competition in the past five years.
"The deadline for the negotiations has been postponed to at least June 30," the source told Reuters. The exclusive period of the talks was previously scheduled to expire on June 20.
Talks were however expected to continue on Monday in Milan when Fininvest meets representatives from the Chinese consortium, the source added.
Berlusconi is due to undergo surgery on Tuesday to replace a defective aortic valve after he was admitted to hospital last week.
Chinese electronics retailer Suning Commerce Group Co Ltd last week agreed to buy nearly 70 percent of the club's local rivals Inter Milan for 270 million euros ($307 million) in the highest profile takeover of a European team by a Chinese firm.
(Reporting by Giulia Segreti; editing by Giselda Vagnoni and Keith Weir)
