Ighalo has taken the Premier League by storm this season, scoring 15 goals.
The 26-year-old is under contract at Vicarage Road until 2020 after penning fresh terms in September.
He previously revealed he would be unable to reject an approach from United.
“There has been speculation from Spain and Italy but I’ve played there and now want to play in England,” he told The Sun.
“I don’t think I will be moving but I’m not sure I’d say no if United called.
“They were my team growing up. I loved watching Andy Cole and Dwight Yorke on TV.
“They were my idols and playing at Old Trafford has always been a dream.