They have contacted the Championship side over Sarr, sources told ESPN, and are at the enquiry stage of the deal, with a fee still to be negotiated.
Jurgen Klopp has quickly moved this week to bolster his side with midfielder Thiago Alcantara set to arrive from Bayern Munich and has now turned attention to Sarr to bolster their forward line. They were strongly linked with Timo Werner earlier this summer, but he ended up joining Chelsea and Klopp is still keen to add a further player to his attacking options.
Sarr, 22, joined Watford from Rennes in June 2019 for £30 million on a five-year deal. He made 30 appearances last season, scoring six goals, but with Watford relegated, the club have already seen several players leaving with Pervis Estupinan joining Villarreal this week and Abdoulaye Doucoure departing for Everton.
If Sarr ends up joining Liverpool, he will bolster a formidable forward line up which includes Mohamed Salah, Sadio Mane, Roberto Firmino, Takumi Minamino and Divock Origi. Liverpool's other summer signing was bringing in left-back Konstantinos Tsimikas from Olympiakos for £11.7m.
Liverpool have a proven track record of signing players from lower Premier League clubs or Championship sides and integrating them into their first team. Andrew Robertson was signed from Hull City, Mane from Southampton, Xherdan Shaqiri from Stoke City, Adam Lallana (now of Brighton) from Southampton and Georginio Wijnaldum from Newcastle.