"He is one of my best friends, and he is my neighbour as well," Lukaku told the club website (www.manutd.com). "We are always together on a daily basis so he would explain to me how things were going.
"When he signed for United, to have witnessed that, it really triggered something in my brain and I knew that if one day I had the chance to sign then I would not say no."
Pogba last week posted pictures with Lukaku on social media, calling himself 'Agent P'.
Lukaku finished runner-up for the league's Golden Boot award last campaign with 25 goals and was tipped to return to champions Chelsea but chose to reunite with manager Jose Mourinho on a five-year contract.
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Everton manager Ronald Koeman believes the striker made the right choice.
"We know it was one of the challenges for Lukaku," Koeman told reporters.
"He took the right decision and lets hope everything goes well for him because I like him. I like the player but now it's about Everton."
Lukaku trained with United's squad on Monday ahead of their U.S. tour which begins with a match against LA Galaxy on July 16.
(Reporting by Aditi Prakash in Bengalur; editing by Amlan Chakraborty)
