PERTH, Australia -- Serena Williams and James Blake won singles matches and then teamed for a mixed doubles victory Wednesday, leading the United States past defending champion Spain 3-0 in the Hopman Cup.

Williams beat Virginia Ruano Pascual 6-3, 6-3, and Blake defeated Tommy Robredo 6-3, 6-0. Williams and Blake downed Pascual and Robredo 6-1, 6-4 to end Spain's chances of making the finals.

The Czech Republic edged Italy 2-1 in Group B. Australia and the Czech Republic, both 2-0, will meet Thursday.

The Americans play Belgium on Friday, with the winner most likely to represent Group A in Saturday's final. The match will feature a replay of the WTA Championships final in which Kim Clijsters beat Williams in Los Angeles -- Clijsters' first win over Williams in six attempts.

Williams said she was exhausted in Los Angeles after winning eight of 13 tournaments, including the French Open, Wimbledon and U.S. Open on the way to a 57-5 record in 2002.

"Mentally I was shot and physically I was dead," she said. "I just needed a break because I had played too much."

Williams is trying to become the fifth woman to win four straight Grand Slams. The Australian Open starts Jan. 13.

"I'm far from my best right now," she said. "I haven't begun to play my best at all, so I have a long way to go. I'm sure everyone is excited to hear that."

Blake handed Robredo his first loss in six singles matches over two years in Perth.

"I picked up my game a lot from the first match, so I'm feeling pretty confident," Blake said. "Hopefully it can keep going."

In Group B, Jiri Novak beat Italy's Davide Sanguinetti 6-7 (10), 7-5, 7-5 to set up a deciding mixed doubles after Silvia Farina-Elia had defeated Daja Bedanova 6-4, 2-6, 6-2 to put the Italians up 1-0.

Novak failed to convert on six set points before losing the first-set tiebreaker. He then teamed with Bedanova to win the doubles 6-3, 6-3, with the last seven games going against serve.