The 21-year-old, who signed from Dalian Shide for £3.5m in January 2004, will head to England next month.
Since signing for United Dong has been on loan at Belgian feeder club Royal Antwerp, during which time he has won seven caps for the China national side.
"The boy has a big chance" United manager Sir Alex Ferguson told MUTV.
Dong has made a few appearances for United on a couple of pre-season tours
The striker will be one of seven loan players to return to Old Trafford in January.
Lee Martin and Phil Bardsley will come back from Rangers, along with Chris Eagles (NEC Nijmegen) and Giuseppe Rossi (Newcastle), plus Jonny Evans and Danny Simpson, who have been playing with Dong at Antwerp.