Tennis star Andy Murray thrilled fans as he made it through to the semi-finals at the US Open for the first time today, but no-one was more excited that his girlfriend Kim Sears.

In a moment reminiscent of Meg Ryan's famous When Harry Met Sally scene, the 21-year-old tossed her head with reckless abandon as she applauded his defeat of Juan Martin Del Potro.

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Delight: Kim Sears cheered on boyfriend Andy Murray at the US Open in New York

Meg Ryan moment: Kim's excitement was reminiscent of When Harry Met Sally's most famous scene

The gorgeous blonde, the daughter of top tennis coach Nigel Sears, has been dating the star for more than two years and has been credited with melting the usual reserve and dour expression of Misery Murray.

She is expected to once again cheer from the stands as the Scot faces world number one Rafael Nadal.

Murray defeated 17th seed Del Potro 7-6, 7-6, 4-6, 7-5 after three hours and 58 minutes of tense combat, with the 19-year-old Argentinian reduced to tears of frustration in his post-match interview.

Number one fan: Kim and Andy have been dating for more than two years

However he will now have to raise his game  when he takes on Nadal, who defeated him in straight-sets defeat in this year's Wimbledon quarter-finals.

He remains upbeat about taking on the champ, saying: 'The one thing that I need to improve is to return better. If I take the Wimbledon match away, then in the times I have played him on hard courts, there have been a few close sets and really tough matches.

'It comes down to who returns better and who gets the breaks of serve.

'Normally that's the best part of my game. How you do in Slams is how you're remembered in tennis, and I wanted to improve my record in them this year.' 

Victory: Andy celebrates getting through to the semi-finals at the US Open