US tennis superstar Serena Williams on Sunday declined comment about an ongoing probe into her abusive outburst at the US Open, but said she loved the game and would not give up her fighting spirit.

Former top-ranked tennis player Justine Henin will announce her comeback to competitive tennis on Tuesday according to two top Belgian newspapers.

A hand-painted sign in Juan Martin del Potro's hometown of Tandil summed it up: "Welcome to the capital of tennis."

US fourth seeds Serena and Venus Williams won the US Open women's doubles title on Monday, defeating top seeds Cara Black of Zimbabwe and Liezel Huber of the United States 6-2, 6-2.

Serena Williams apologized on Monday for the abusive and threatening tirade she launched at a line judge in a semi-final loss to eventual champion Kim Clijsters at the US Open.