Norfolk is hoping to retain his Paralympic crown in Beijing next year

Norfolk, who has been sidelined for four months with a shoulder injury, beat Hunter 6-4 6-3 in his opening round-robin match.

David Wagner edged out fellow American Nick Taylor 6-3 5-7 6-4 in Thursday's other quad match.

It is the first time that quad events have been included at the US Open.

Norfolk, the Athens Paralympic gold medallist, has played just other two tournaments so far this year.

During that time he has seen his American rival Wagner succeed him as Japan Open and British Open champion and also take the world number one ranking.

Wagner remains the only player to have beaten Norfolk in singles competition since July 2003.

In the men's singles, world number one Shingo Kunieda thrashed Japenese compatriot Satoshi Saida 6-0 6-2.

World number two Robin Ammerlaan began the defence of his title with a 7-6 7-5 win over fellow Dutchman Ronald Vink.

In the women's singles, world number one Esther Vergeer brushed aside Dutch compatriot Korie Homan 6-4 6-2.