Popular tennis ace Roger Federer has long wooed fans for his silky-smooth skills but his off-court antics at the US Open have earned him even more hearts.

Shortly after defeating American John Isner in straight sets in the fourth round of the Open, the 17-time grand slam champion stopped to sign autographs for adoring fans.

But the autograph session came to an abrupt halt when crowds in the stands pushed forward, crushing a little boy at the end of a row close to the world No.2.

Federer immediately asked security to pull the boy out while they attempted to quell the rest of the fans.

In trademark Federer fashion the Swiss comforted the boy and signed his hat and tennis ball.