The 28-year-old is expected to sign for the Rams after completing a medical and has discussed personal terms with Derby chairman of football Adam Pearson.

Blackwell said: "We have agreed a figure with Derby and Rob has travelled to speak to them."

The Blades turned down an initial offer from Derby earlier in the summer, but have accepted an improved bid, reported to be £1.6million rising to £2million with add-ons.

Hulse, who has a year left to run on his Blades contract, started out at Crewe before big money moves to West Brom, Leeds and then Sheffield United.

The Blades paid £2.2million for Hulse in July 2006, but his first-team appearances were limited last season after his recovery from a broken leg sustained at Chelsea in March last year.