Manchester United summer-signing Romelu Lukaku says that he aims to reach the levels of world-class strikers like Cristiano Ronaldo and Robert Lewandowski in the future.

The Belgian, who has joined United in a £75m move, has already scored two goals in United's pre-season tour to the US.

"I'm 24, so can't say I'm the complete package," he said. "I can't say I'm in my prime. 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.

"I'm far from the level of Ronaldo and Lewandowski. That's the level I want to aim for. How do I reach that level? Keep improving. 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."