The Netherlands striker has emerged as a surprise target for United as Erik ten Hag looks to bolster his forward options after Cristiano Ronaldo’s departure.
United’s budget may only stretch to loan signings after they spent more than £200 million in the summer and Besiktas borrowed Weghorst from Burnley for the season after their relegation from the Premier League.
Weghorst appeared to wave farewell to Besiktas supporters after Saturday’s 2-1 victory over Kasimpasa.
“I don’t understand why Weghorst said goodbye to the fans, why he made such a move,” Besiktas sporting director Ceyhun Kazanci told Fanatik.
“He is our player right now. Our contract expires at the end of the season.
“If Manchester United or any other team wants Weghorst, they will meet with Burnley anyway.
“There could be a reward for us if we give our consent to the cancellation [of the loan].
“For example, if Burnley told us: ‘Weghorst is moving to this team and we are giving you half of the fee’ we would sit down and talk to them.”
Weghorst, who joined Burnley last January, only scored two goals in 20 games as they went down to the Championship.
But he has struck nine times for Besiktas and scored twice as a substitute against Argentina in the World Cup quarter-final. He has also scored 17, 16 and 20 goals in Bundesliga seasons with Wolfsburg.