Harley, a free transfer from Premiership side Fulham on a three year deal, but will officially join on 1st July as this is when his Craven Cottage contract ends.
JON HARLEY - FIRST SIGNING OF 2004-05 SEASON.
Warnock sufc.co.uk, the Blades official website: "Jon performs best when he is happy in his environment, and I think it's true to say he hasn't been over the last few years.
"That's what he needs right now and I am expecting him to compliment our left side.
"He has taken a big drop in wages to come here but I can't see anything but good times ahead for him."