Novak Djokovic warmed up for the US Open by dancing with a lawn mower, and now he is responding to marriage proposals from fans.

The world number two, amused by a boy's (sarcastic?) yell, went over to the spectators and invited his admirer to hit a a few serves during his practise session.

Djokovic, seeded second, faces Paolo Larenzi in his first match on Tuesday as he looks to defend his Flushing Meadows title to win his second Grand Slam of the year.

The 25-year-old defeated Rafael Nadal in January's Australian Open final but was defeated by the Spaniard as he bid to hold all four major titles in the men's game at Roland Garros.

Roger Federer then defeated Djokovic at Wimbledon in the semi-finals before Andy Murray was triumphant over the Serb in the last four of the Olympics event.