It had also been claimed that Manchester City installed a buy-back clause in the £10million deal that took him to Dortmund from the Etihad in 2017.
However, Watzke insists that is not the case and warned United they will fave a losing battle in trying to sign the 19-year-old.
Asked about the rumours surrounding his star player’s future, he said: “I don’t care about that. Everybody knows that Jadon will play for us next year.
“That’s a fact and we don’t have a price tag for him. And because everybody in Europe knows that nobody contacted us.”
On a potential buy-back clause for City, he added: “We never give information about contract details but City has no co-determination right at all.”
Sancho is set for a starring role when Dortmund face rivals Bayern Munich at the Allianz Arena tomorrow evening (5.30pm kick-off).
Dortmund are currently top of the Bundesliga and two points above Bayern as they go in search for their first league title since under Jurgen Klopp in 2012.
Sancho has scored eight league goals this season and has a Bundesliga-high 13 assists.
A win tomorrow night would give the leaders an enormous advantage for the run-in but manager Lucien Favre says nothing will be decided tomorrow whatever the result.
“This game is very special, Bayern v Dortmund,” he said. ”The table is close, seven games remain, and two great teams.
“If we win, nothing is decided, if we draw, nothing is decided, if we lose nothing is decided…it is completely open.
“Like all teams, they do have some weaknesses. Every team has that, even the best teams in the world.
“But [they do not have] too many, not many. And they have a lot of strengths of course, we know that.
“We have to concentrate on a lot of things.”