"We have of course had communication with Manchester, but everything there is to say on the subject has already been said by us," sports director Michael Zorc said.
"That will not change in the next three days."
Dortmund reportedly rejected a formal bid from United of up to €100 million $165 million).
Sancho, 20, who scored 17 goals in the Bundesliga last season, has been a long-term target for United as it looks to build on finishing third in the Premier League last season.
It's unclear whether Sancho will be fit to play Freiburg at home in the Bundesliga on Sunday (AEST), having also sat out Thursday's (AEST) 3-2 defeat away to Bayern Munich in the DFB Super Cup showdown.
"Jadon has a slight cold, we'll see," coach Lucien Favre said, with Sancho so far having tested negative for the coronavirus earlier in the week.
So far in 2020-2021, Dortmund has beaten fellow UEFA Champions League side Moenchengladbach a fortnight ago, but crashed to a 2-0 defeat at Augsburg last weekend before losing to Bayern in the cup clash.