Lukaku, 24, was due to have an overnight medical at the UCLA campus in California ahead of his switch from Everton.
Old Trafford boss Mourinho will land the Belgian in a classic coup that blind-sided the Blues — with the striker agreeing a five-year deal worth £250,000 a week.
United switched targets after Real Madrid refused to compromise on their £85m valuation for Spanish striker Alvaro Morata.
I think Lukaku will be perfect for us, and also a proven goalscorer in the premier league. If it wasn't for Harry Kane scoring so many in the last 2 games of the season he would have won the golden boot!
Wow. He can be great alongside Ibrahamovic. He also take on defenders which is a great quality
Ibra has left due to his injury. I think he'll be joining LA Galaxy next, shame.