Romelu Lukaku said he was delighted to be moving to "the biggest club in the world" after Manchester United agreed a fee to sign the Belgium striker from Premier League rivals Everton.
United said on Saturday they had agreed a fee for Lukaku with the Merseyside club, which was reported by British media to be an initial 75 million pounds ($96.68 million).
British media said on Sunday that Lukaku had completed his United medical in Los Angeles.
The Belgian is set to become the Old Trafford club's most expensive signing since last year's world record deal for France midfielder Paul Pogba, who rejoined the 20-times English champions for 89 million pounds from Juventus.
"Who would say no to the biggest club in the world?", Lukaku told ESPN in an interview.
"When (Manchester United) came calling, I didn't have to think twice. So I'm really delighted to hopefully be part of their history.
"Best stadium in England. The best fans. This is the perfect opportunity. I always said I wanted to play for a team that's challenging for every trophy that there is."
United manager Jose Mourinho was in charge at Chelsea when Lukaku was sold to Everton in July 2014.
Lukaku, however, will arrive at Old Trafford looking for a fresh start and is keen to learn more from the Portuguese coach.
"(Mourinho is) a guy who I wanted to play for since I was 10 years old, so now to have the opportunity to work under him again is great," Lukaku added.
"We've been in contact. He explained to me what the club was like, what he expects from me. He sees the maturity that has grown throughout the years, so I'm really thankful for the opportunity he gave me again."
Lukaku was the second-top scorer in the Premier League last season with 25 goals for Everton, attracting interest from both United and Antonio Conte's English champions Chelsea, who British media reported had matched United's offer.
He is one of three players to have scored more than 10 goals in each of the past five English top-flight seasons alongside Arsenal's Olivier Giroud and Manchester City's Sergio Aguero.
United are hoping to confirm the deal before they depart for a pre-season tour to the United States on Sunday.
($1 = 0.7758 pounds)