The deal is now awaiting English FA approval.
United agreement with his parent club Shanghai Shenhua officially expired on Sunday night.
But according to The Telegraph, both sides have agreed for the 30-year-old to stay in Manchester until the new year.
The newspaper said Ighalo will discuss a new contract with Shanghai Shenhua once he returns in 2021.
Ighalo’s agent Atta Aneke had hinted that talks were in place for the ex-Watford man to remain at Old Trafford.
Aneke told Nettavisen: “We are nearing an agreement with Manchester United on an extended loan.
“The agreement will mean that Ighalo will remain with them until January 2021.”
Ighalo swapped the Chinese Super League for the Premier League in a shock deadline day loan deal back in January.