Despite Everton sources claiming to ESPN FC on Thursday that no deal had been agreed with United for the Belgium international -- raising Chelsea's hopes of beating United to the 24-year-old -- senior figures at Old Trafford believe that the player is now on course to join United.

Plans have been made by United for Lukaku to undergo a medical in Los Angeles, where he is spending his summer vacation, and the formalities could be completed by Friday afternoon, enabling a deal to be sealed before Mourinho's tour squad jets out of Manchester for California on Sunday.

Wayne Rooney, meanwhile, is expected to stay behind in order to complete a return to Everton after being given permission by United to negotiate a move back to Goodison Park, 13 years after leaving the club for Old Trafford.

Mourinho's team had been led to believe Lukaku favoured a return to Chelsea and that a deal to take the Belgian back to Stamford Bridge had, at one stage, been close.

The club had also baulked at Everton's valuation of £100m and were convinced Real Madrid striker Alvaro Morata would cost significantly less.

However, reaching an agreement with Real Madrid for Morata has proved more difficult than originally thought with the Spanish side holding out for close to £80 million.

The United manager knows Lukaku from his time in charge at Chelsea. It was Mourinho who sanctioned Lukaku's sale to Everton in 2014.

The 24-year-old has become one of the Premier League's most prolific strikers in his three seasons at Goodison Park, scoring 71 goals in 133 games.

Everton were desperate to keep their main goal scorer, especially after spending close to £100 million this summer to help Ronald Koeman's side break into the top four.

However, Lukaku has made no secret of his desire to play in the Champions League.