Liverpool went into the match in the Bank of America Stadium having already qualified for Monday's final against Manchester United, after Manchester City lost to Olympiacos in a penalty shootout in Minneapolis earlier in the day.
Allen opened the scoring for Liverpool after 17 minutes, and it was a goal the Welshman made himself after he robbed Michael Essien 25 yards from goal.
His initial shot hit the post, and Milan goalkeeper Christian Abbiati saved Raheem Sterling's follow-up effort, but the £15m signing from Swansea City showed great technique to volley home the rebound.
Suso then doubled the lead with a minute to go with a curled left-foot finish following a one-two down the left with Philippe Countinho.
'16 - GOAL: Joe Allen nicks the ball 25 yards out after a mistake from Essien, and although his initial shot hits the post, and Abbiati saves Sterling's follow-up effort, the Wales midfielder is able to net the rebound.
‘27 - PENALTY: Rami brings down Sterling, who was running away from goal after the pass from Lambert.
‘28 - PENALTY SAVE: Lambert's penalty is far too close to Abbiati and the Milan goalkeeper saves.
‘38 - SAVE: Niang cuts in from the right and shoots left-footed, and Mignolet saves, if a little uncomfortably.
‘77 - SAVE: Honda chips over the top for Niang but Mignolet is out smartly to block. What a pass from the Japan international!
‘89 - GOAL: What a great finish from Suso. The Spaniard sets up Coutinho down the left, and when he receives the ball back, he gently curls a finish past Gabriel from the edge of the area.
‘90+2 - SAVE: Cristante runs through on goal and shoots, but Mignolet makes a fine one-handed save.
2014, Stephan El Shaarawy, Milan-Liverpool, AFP
Does Suso stay or does he go? The 20-year-old came on at half-time in Charlotte, and impressed in his 45 minutes at the Bank Of America Stadium. He spent last year on loan at Almeria, but, with Luis Suarez gone, manager Brendan Rodgers may think carefully about allowing the Spain Under-21 international on another loan to La Liga, especially as he qualifies as a home-grown player for the Champions League.
MAN OF THE MATCH
M'Baye Niang (AC Milan): Most of the Milan players looked uninterested, past it, or both. Not Niang - the 19-year-old constantly worked the channels to make himself available, looked quick and comfortable on the ball.
Liverpool: Mignolet 6, Kelly 6, Toure 6, Coates 6, Robinson 6, Lucas 7, Henderson 7, Allen 7, Lambert 6, Ibe 6, Sterling 7. Subs: Johnson 6, Enrique 6, Gerrard 6, Coutinho 7, Sakho 6, Can 6, Suso 8, Coady 6, Skrtel 6, Peterson 6.
AC Milan: Abbiati 6, Abate 7, Bonera 7, Rami 7, De Sciglio 6; Essien 5, Muntari 5, Saponara 6; Niang 8, Pazzini 6, El Shaarawy 6. Subs: Gabriel 6, Balotelli 5, Honda 7, Mexes 6, Cristante 5, Albertazzi 6, Poli 6, Zapata 6.
- Sports & Recreation
- AC Milan
- Christian Abbiati
- Michael Essien
- Raheem Sterling
- Rickie Lambert