The French club told PA Sport that 23-year-old Bellion, who has been on loan at Upton Park from Manchester United, would sign his contract on Monday afternoon.
A Nice spokesman said: "The transfer of David Bellion to Nice is confirmed as of this morning. He will sign at 3pm (2pm GMT) which will be followed by a press conference. He will sign on loan until the end of the season with a view to a permanent move."
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