The Americans, who have 15 grand slam titles between them, are in opposite sides of the draw and both have looked imperious so far in swatting aside their opponents with ease.

They are also playing doubles together and could emulate their feat in Sydney when between them they scooped the golds in singles and doubles.

"I mean, that would be fantastic," Wimbledon champion Venus, who won the singles in Sydney, told reporters after beating Czech Iveta Benesova 6-1 6-4.

"Obviously, it's a long way away, but the third round makes it closer. I'm really excited for both of us to be playing really well for the U.S., then trying to play great doubles."

Serena eased into the third round when she needed just 44 minutes to blow away Australian Samantha Stosur 6-2 6-0.

"It's an honour to compete in the Olympics. It's been great," Serena told reporters. "I'm playing for a medal, but I have to get there first. That will be the ultimate goal for me."