Tonne, 20, has made four substitute appearances for the Blades this season, scoring two goals, having signed from Strindheim in April 2011.
Earlier in January he recently signed a contract extension with the Blades until the end of the 2014 season.
The Blue Square Bet Premier side currently sit in fourth place as they bid to return to the Football League.
Source: BBC Sport
Source: FOOTYMAD
