The Williams sisters never lost serve in the 89-minute match in winning their second Open doubles title, and third grand slam crown of the year after doubles triumphs at the Australian Open and Wimbledon.  They will share a winner's prize of $420,000.

"I have a great partner. I believe in her just as much as I believe in myself," Venus said in a courtside interview. "There's nothing like having that on the court."

Serena, meanwhile, apologised for her angry outburst aimed at a lineswoman during her semifinal match against Kim Clijsters at the US Open.

Williams issued a statement on Sunday concerning the incident but while she conceded she had "handled the situation poorly," she did not apologise to the lineswoman or Clijsters.

"I want to amend my press statement of yesterday, and want to make it clear as possible -- I want to sincerely apologise FIRST to the lines woman, Kim Clijsters, the USTA (US Tennis Association) and mostly tennis fans everywhere for my inappropriate outburst," she said.

"I'm a woman of great pride, faith and integrity, and I admit when I'm wrong.

"I need to make it clear to all young people that I handled myself inappropriately and it's not the way to act -- win or lose, good call or bad call in any sport, in any manner."