The Argentine, who joined Liverpool from Brighton on a five-year deal in June 2023, spoke out before Wednesday's Champions League game against Atletico Madrid after watching team-mates Dominik Szoboszlai and Ryan Gravenberch sign contract extensions this year while his own situation remains unresolved.
"I received the news that the club was not in a position to offer me a new contract, which, of course, makes me very, very sad," Mac Allister said.
"Everyone can see that I give my 100% for this football club every single day in training and games. Of course, I can have very good games and bad games, like everyone, but I always give my best. I see Dominik and Ryan renewing their contracts and that makes me very happy because they deserve it.
"At the same time it makes me a little bit sad that I didn't get mine. Of course, there is still time."
Mac Allister, who has been linked with a move to Manchester City, said he had not had any direct contact with the club over the decision not to extend his deal, despite helping Liverpool win the Premier League title and going through difficult periods together.
"We won a Premier League together, we went through difficult times together and I always give my best so we will see what happens," he said. "I don't think I have to prove something, but I have to show the level I can perform and, hopefully, that's the case. I love this club. I love the fans. I know very well this is an amazing club and this city has something very special. I love being here."
He confirmed he had turned down the chance to leave Anfield during the transfer window.
"There were options to leave this summer. I think right now I'm in the right club and I have the right mindset to give 100% for this club," said the World Cup winner, who helped Argentina lift the trophy in 2022.
Head coach Andoni Iraola, appointed in the summer following Arne Slot's sacking, played down any suggestion of a rift over the contract impasse.
"We all have personal situations with different contracts," Iraola said. "The important thing is he wants to be here. We haven't been together a long time but he has been an important player and I rate him very highly. There is still a lot of time to talk about those contract situations."
Mac Allister has been a near-ever-present for Liverpool since his arrival, and his versatility across midfield has made him a key part of Iraola's early plans, even as the futures of Szoboszlai and Gravenberch have now been secured for the long term while his own remains open.