Andy Murray has admitted that he must improve on his sluggish start against Marin Cilic if he is to defeat Tomas Berdych and reach the US Open final.

The British number one came from a set-and-a-break down to beat Cilic in four sets and advance to a semi-final clash against Berdych, who surprisingly eliminated Roger Federer to make the last four at Flushing Meadows.

Despite not having the 17-time Grand Slam champion to negotiate in the semis, Murray has insisted that Berdych has the attributes to cause him real problems on Saturday evening.

"He's a huge, huge hitter of the ball. Even if you want to dictate points and be aggressive, he can take that away from you because he's such a powerful guy," said Murray.

"You need to be smart against him. You need to use good variation and try not to give him the same ball over and over, because he likes that.

"I'll fight from the first point to the last. If I do that, I'll give myself a shot. But I can't afford to start like I did [on Wednesday night], that's for sure."

Czech Berdych has beaten Murray in four of their last six meetings.