Balotelli's representatives are in talks with the Anfield club after a £16m fee was agreed with Milan, but the player is yet to fly to England for talks over personal terms and any added clauses about his behaviour.
That would make a debut this weekend against former club Manchester City very unlikely as he needs to be registered by midday on Friday to be eligible for Monday's match.
Liverpool approached the Serie A club about the striker's availability just weeks after Brendan Rodgers denied making a move, and it appears things are moving along quickly.
Milan confirmed the 24-year-old's departure and Balotelli, who said goodbye to his San Siro team-mates and backroom staff on Thursday, said: "Today is my last day at Milan. I am going to Liverpool."
Rodgers has made no secret of his wish to bring in a new forward following Luis Suarez's summer departure, but any chance of Balotelli coming appeared dead in the water earlier this summer.
Speaking on Liverpool's tour of the United States, Rodgers said: "I can categorically tell you Mario Balotelli will not be at Liverpool."
Rodgers was instead targeting Monaco's Radamel Falcao, but the Colombia striker's preference is a move to Real Madrid.
Balotelli's three seasons at City were blighted by trouble, on and off the field, although he did manage 30 goals for the club in all competitions.
Sky Sports pundit Jamie Carragher has questioned whether Balotelli would be an automatic starter at Anfield.
"They definitely need a striker, there's no doubt about that," he told Sky Sports.
"At the moment they only have Daniel Sturridge and Rickie Lambert - it looks like Fabio Borini is going to move on - and you need strikers.
"Would he be the final piece of the jigsaw? Would he make the starting XI if everyone was fit and firing? Who knows?
"At the moment Daniel Sturridge has got 36 goals in 50 games for Liverpool and at this moment he is the main man up front.
"Would Brendan then accommodate another striker, whoever that may be, like he did with Luis Suarez?
"He has lots of options now, Brendan Rodgers, and I don't think he will play the same team too often so they do need those options."
Liverpool play Manchester City on Monday Night Football from 7pm on Sky Sports 1