The 23-year-old is training alone following his public row with Ten Hag in the aftermath of the 3-1 defeat to Arsenal before the international break.
Sources have told ESPN that Sancho has not apologised for his role in the spat and, speaking at a news conference on Friday, the United manager refused to say whether the England international remains part of his long-term plans at Old Trafford.
"I don't know," said Ten Hag, when asked whether Sancho will play for United again.
"I prepare my team the best I can, I put all my effort into the players who are available. He is not available, so in this moment, he is not important, because he can't contribute."
Sancho has been banished from first-team training after publicly challenging Ten Hag's reasons for dropping him for the game at Arsenal.
Ten Hag said it was because of poor training performances, before Sancho issued a post on social media to say the comments were "completely untrue" and that he had been "made a scapegoat for a long time."
Sancho is unavailable for Brighton's visit to Old Trafford on Saturday but Ten Hag insists the rest of his players are focused.
"With fans it's the talk, with you [the media] it's the talk, but with the players it is not the talk," he added.
"They want to perform. For players who didn't have so much opportunities, they get their opportunity, so this is their chance to come into the team.
"So, as I said, we had a really good spirit, everyone is focusing on this game, and the coming games."
Sancho is currently training alone with club staff and there is no timeframe for his return to the squad.
Ten Hag is also without Antony, who has been given a leave of absence amid allegations of abusive behaviour towards multiple women. Raphaël Varane, Mason Mount, Luke Shaw, Tyrell Malacia and new signing Sofyan Amrabat are all out injured leaving United short of options, but Ten Hag insists he had no choice but to take a tough stance on Sancho.
"It's in favour of the team," he said.
"That is what my decision is based on. That is not about me, and to be strict. No. This is in favour of the team."