Lukaku joins football's list of biggest transfers

Lukaku arrived from Everton in a deal reportedly worth $123.1 million, having scored 25 Premier League goals last season and 53 in total after leaving Chelsea in 2014.

The Belgium striker has already netted twice on the pre-season tour of the United States – scoring against Real Salt Lake and Manchester City.

However, the 24-year-old said he still has room for improvement as he tries to reach the level of four-time Ballon d'Or winner Ronaldo, who scored more than 100 goals as he claimed three Premier League titles and the UEFA Champions League during his six seasons at United.

"I'm far from that level. But it's the level I want to aim for. I'm 24, I can't say I'm the complete package. I can't say I'm in my prime," Lukaku said.

"There is a lot of work to be done and I'm delighted that there is still work to be done. That means I can become even better than I am.

"That's the state of mind I have - I always want to be better. There is always room to improve. I just want to become the best player I can be.

"I'll never say it's good enough. It's a pressure I put on myself. When you play for United you have to perform every week."

After comparisons with former Chelsea striker Didier Drogba were raised, Lukaku said: "I'm different.

"Drogba is more of a hold-up player, a target man. I prefer to have ball to feet and run in behind. We're totally different.

"We might have physical similarities but we're totally different players. I'm Romelu Lukaku, I want to create my own history. I'm at United, he was at Chelsea."

United won the Europa League and EFL Cup last season but have not tasted Premier League glory since 2012-2013 and Lukaku said: "The manager has a masterplan and we are following his plan.

"For me it's all about winning. I want to win. Now I'm at a club where winning is the most important thing. It's something inside of me. I want to help my team-mates deliver wins game in game out.

"That's what I came here for [trophies]. Manchester United, for me, equals trophies. The biggest club in the world equals trophies.

"Growing up, I've seen United win the league every year, almost! You want to be a part of that history. It's drilled into your head when you do training sessions with the players, you don't want to be on the losing side.

"That is something that I wanted to feel. I wanted to feel that pressure, I wanted to feel that hunger – to be here now. I'm grateful to be part of the biggest club in the world, but there is a lot of work to be done, and I know that I need to work much harder than I have until now.

"I want to do it because, at the end of the day, I want the club to reach bigger heights, I want the players to win a lot of trophies and I want to create history with the club."