The Nigerian has been a sensation since arriving from Shanghai Shenhua in January scoring in all his competitive starts for the team.
Ighalo is wanted by United permanently, but the Daily Star claimed they do not want to sign him on his existing £300,000-a-week wages.
They would prefer to pay him closer to £100,000-a-week, as it would be in line with his place as a rotation player in the squad, although some reports suggest that Red Devils could pay as much as £200,000-a-week.
The 30-year-old must now decide if he wants to continue playing for the club he has supported as a child, or if he prefers the financial security of his Shenhua contract.
His loan deal expires on May 31, but that may be extended by FIFA depending on if and when the existing Premier League season is concluded.
Ighalo recently claimed that he was enjoying his time at United and was open to staying permanently, if a deal could be agreed.