Liverpool boss Jurgen Klopp is a big fan of Sarr and wants to take him from Vicarage Road before the transfer window closes.
The winger is also keen on the move, but Watford are demanding a fee of £40m and Liverpool want to bring in cash to finance a move.
Brewster is attracting attention from a host of clubs, with Sheffield United now having spoken to the striker’s entourage about a switch to Bramall Lane.
Crystal Palace and Aston Villa also remain keen and could make a move for Brewster.
Liverpool will sell the striker if the offer is right and it is claimed that the bidding is now due to begin, as the race heats up.
Brewster, 20, spent the second half of last season on loan in the Championship at Swansea City and impressed.
He scored eleven goals in 22 appearances for Swansea last term and was involved with Liverpool in the Community Shield this term.