Andy Murray has admitted that recent injuries have left him feeling 'frustrated' on the court.

The 27-year-old, who had to undergo surgery on his back last year, struggled with cramp against Robin Haase in the US Open first round on Monday, eventually progressing to the next round where he will face Germany's Matthias Bachinger.

"I think if you have a physical issue that's hampering you, it's very easy for that to take over your thinking when you're on the court," Sky Sports News quotes Murray as saying.

"It's frustrating to not be able to do the things that you want your body to do and that distracts you from what you should be doing on the court, which is trying to beat your opponent, not how you have to move to your backhand side or your forehand side or whatever the issue is."

Murray won the US Open in 2012.