Andy Murray has admitted that the upcoming Davis Cup is playing on his mind and has altered his training regime after progressing to the fourth round of the US Open.

Murray beat Thomaz Bellucci in straight sets to advance to the last 16 as he looks to improve upon his quarter-final performance at last year's tournament.

While the world number three accepted that the Davis Cup remains a big priority, he revealed that he is concerned that he could be "flat" by the time his commitments in New York are over.

"Obviously if I was to lose in the next round I would have more time to prepare for the Davis Cup, which is a big priority between now and the end of the year," he told The Guardian. "But ideally I would be going into the Davis Cup having played on the [last] Sunday here.

"I don't feel more stressed by it, but I have had thoughts about it. Obviously I have played a lot of tennis and I am thinking that maybe by the time I get to the Davis Cup I could be flat or even here towards the end of the tournament.

"I hope that is not the case because I did plan it with my team about my training and stuff so that that would not be the case. But you always have thoughts like that about big events, especially with the Davis Cup."

Murray faces a clash with 15th seed Kevin Anderson in the fourth round.