The 26-year-old former England striker only joined United in the summer but has struggled all season.
City are 12th place in the table, two places behind Leeds and his arrival suggests that Ade Akinbiyi, who has been linked with a move to Sheffield United, could be about to leave.
The ex-Bolton and Middlesbrough frontman has made nine league starts at Elland Road, scoring just one goal in the league cup win against Swindon.