The likes of Marcus Rashford, Kobbie Mainoo and Alejandro Garnacho could all be moved on to fund manager Ruben Amorim's summer market plans.
But Beckham told the Athletic: “I think Ruben definitely needs to be backed in bringing in the players he wants but I actually don’t know how possible it is. I don’t speak to Jim that often, only from time to time.
"Ruben needs to be backed as a manager to bring in his team and his philosophy; he’s trying that already but I think once he brings his team in and his players, then you’ll see something different.
“I’d like to think you wouldn’t have to sell your captain (Fernandes). He has been exceptional.
"We’ve all been critical at times of some United players — but when we needed someone to step up, he has done it."
Don't sell the academy players
The Inter Miami co-owner also said: “I also hate (the idea of) any young player who has grown up at United leaving the club. We shouldn’t be selling players purely for financial reasons.
“It should be what they are doing on the field and if they’re not performing, there’s always a chance — we all knew that, I knew that. If I wasn’t performing on the pitch, it didn’t matter what I’d done in the past or what I was going to do in the future; there was a good chance that I was either going to get left on the bench, or I was going to get sold."
Beckham added: “I’d like to think that Manchester United don’t sell players that have grown up at the club, understand and love the club. I don’t want to see players leave Manchester United if they care about United like I do.”