Pogba's current deal was due to expire at the end of the season but United took up an option of extending it by a further 12 months, meaning the Frenchman is tied to the club until 2022.
However, Pogba's representatives were angered by United's refusal to sit down for contract negotiations before they activated the clause.
And, in an interview with Tuttosport to be published on Tuesday, Raiola has cast Pogba's long-term Old Trafford future into doubt once more.
"I can say that it's over for Paul Pogba at Manchester United," Raiola said.
The agent's full interview is set to be released on Tuesday, on the eve of United's crucial Champions League game against RB Leipzig.
Pogba rejoined United for a then-world record £89m fee from Juventus in 2016 but has been consistently linked with a move away from the Red Devils in the last three years.
The 27-year-old has struggled for fitness and form this season and recently spoke about how the draining effects of coronavirus stayed with him.
Pogba, who scored the equaliser in Saturday's 3-1 win at West Ham to bag only his second goal of the campaign, told MUTV: "It's hard to explain because you wouldn't understand.
"Even in training, I would say to the fitness coach that I feel strange. It's not me. I get tired very fast and I'm out of breath really fast.
"The first game of the season [against Crystal Palace], I couldn't run. I was trying.
"I was very out of breath and it took me a long time to get back to my fitness and to get back physically good."
United need a point at the Red Bull Arena in order to qualify for the knockout stages of the Champions League. Defeat will see them finish third in Group H and drop into the Europa League.
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