Sancho, 20, has been United’s priority target throughout the transfer window but Dortmund are refusing to lower their £108million asking price and with three weeks left in the window, the club have scoured the market for alternative options.
That’s led United to consider Sarr and the Independent claim that talks have been held with the Senegal international’s representatives.
The 22-year-old joined the Hornets for a fee of around £40m and Watford want to recoup as much of that fee as possible this summer following their relegation to the Championship.
Liverpool have kept a close eye on the winger’s situation and Jurgen Klopp is keen to sign the forward as back-up for the likes of Mohamed Salah and Sadio Mane.
However, the Reds spent weeks negotiating a reduced fee for Bayern Munich midfielder Thiago Alcantara and Jurgen Klopp has little left in his budget after a £25m fee was agreed.
Sarr scored six goals in 30 appearances during his debut season for the Hornets last term and was one of the few players to impress as the Hertfordshire club were relegated.