ANDY MURRAY is gunning for Roger Federer as he chases the Swiss across the hard courts of North America and on to the US Open. The Scot will defend his Rogers Cup title in Toronto this week, opening against either Xavier Malisse or Michael Berrer, but he has his sights trained on Federer, the man he could meet in the final.The Swiss is now down to No.3 in the world rankings, one place ahead of Murray, and the Scot aims to overtake him soon. Even so, Murray knows that Federer and his 16 grand slam titles is a huge obstacle in his path as he tries to win this week and then bids to claim his first major trophy at the US Open later this month.Murray said: "I'm going to try and overtake him. He had three or four years where his consistency was incredible but it's nearly impossible to keep that up for seven, eight years. It's very tiring and tough on the body. But I wouldn't say he is vulnerable. I think when it comes to the big tournaments he's still up there with the best guys in the world. When it gets to the those events he'll still feel he can beat everybody. But I want to improve my ranking and the only way to do it is to win tournaments so that's what I'll be focusing on."