The offer values the club the four-times prime minister refers to as "my Milan" at around 700 million euros (548 million pounds) including debt, one of the sources said. The identities of the Chinese investors were not known.
Berlusconi has been looking for more than a year for someone to buy a minority stake in the club that won the Champions League five times after he bought it 30 years ago. It has failed to bring home a Serie A title in the past five years.
The second source said formal talks could only begin with the approval of Berlusconi, who is reluctant to lose control of such a high-profile asset, but he could change his mind.
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"The offer is 700 million euros for the whole club, including debt. They want 70 percent now and the rest in a year or a year and a half," the first source said.
The 79 year-old, whose political influence has been fading since a 2013 tax fraud conviction and subsequent expulsion from parliament, has said his financial resources cannot compete with wealthy Arab and Asian investors buying into European soccer.
Last summer, a group led by Thai businessman Bee Taechaubol signed a preliminary agreement to buy 48 percent of AC Milan, but the parties never reached a final deal. A person who followed the negotiations said Berlusconi changed his mind at the last minute.
Fininvest, the Berlusconi family holding company that also controls broadcaster Mediaset and publisher Mondadori, declined to comment on the offer.
Red and black-shirted Milan had 188.5 million euros in debt in 2015, so Fininvest could cash in around 500 million euros if the deal were to go ahead. The club finished last year with a consolidated net loss of 89.3 million euros.
Small shareholders - fans who hold a tiny symbolic quota - have publicly criticised the club's commercial and sporting management as the trophies stopped coming.
"The red and black fans have been forced to pin their hopes on a turnaround after Fininvest sells," small shareholders association president Edoardo Barone said.
(Reporting by Elvira Pollina, writing by Isla Binnie, editing by Silvia Aloisi and Jane Merriman)
