Brendan Rodgers' side were without Daniel Sturridge for the game as the England striker has returned to the UK for treatment on a minor hamstring injury, although he is expected to be fit for Liverpool's final pre-season game against Borussia Dortmund next Sunday.
Joe Allen opened the scoring after 17 minutes after finishing a move he started when he robbed the Milan defence and tucked home the rebound from Raheem Sterling's saved shot, before Suso sealed the win late on with a low first-time effort from 20 yards.
Rodgers admitted after the game that his immediate target for next season is another top-four finish.
"It's going to be very, very competitive," said Rodgers. "All the teams will have improved as will we, so the first aim is to qualify for the Champions League and then try to build from there. That's what we did last year.
"I think this year we have greater belief. I think we were a surprise for most people last season, but you can see the level of football we are playing. What pleased me tonight was the level of maturity, even with the young players playing. There is a belief we can win games and even in pre-season, creating that mentality is very important."
Liverpool now face Manchester United in the final of the tournament in Miami on Monday night as they prepare for their Premier League opener against Southampton on August 17.
The Reds lost to Roma in the opening game of their US tour before beating Olympiakos and Manchester City.
Watch the International Champions Cup final between Manchester United and Liverpool live on Sky Sports 1 at 12.30am on Tuesday.