Former England Under-19 international Fredericks has been a standout performer for the Cottagers since joining from Tottenham Hotspur in 2015 and he has made 94 Championship appearances.
The 25-year-old has been a key part of the side once again this season and his impressive performances have led Fulham to fifth in the table, seven points behind second-placed Aston Villa.
Reports have claimed a number of teams are showing an interest in the defender but it is West Ham, who are battling against Premier League relegation, that are leading the race.
David Moyes, whose future at the London Stadium beyond the summer is still not sorted, is eager to strengthen his defence if a new contract comes his way and Fredericks is top of his transfer wishlist.
Uwe Rosler was sacked by Fleetwood following a 3-0 reverse at Doncaster which condemned Town to a seventh straight defeat in all competitions.
Cambridge interim head coach Joe Dunne was pleased with how his side adapted to beat Grimsby 3-1.