PERTH, Australia (AP) -- The United States was eliminated from winning the Hopman Cup by Australia after Americans John Isner and Melanie Oudin were beaten in singles matches Tuesday.

Lleyton Hewitt defeated Isner 6-1, 7-5 and Samantha Stosur beat Oudin 6-2, 6-4 to clinch Australia's 2-1 win. Isner and Oudin won the mixed doubles.

The U.S. has won the Hopman Cup five times, but has an 0-2 record in group play and cannot reach the final. Australia is 1-1 in group play.

The Americans play a final round-robin match against Romania on Thursday.

Spain remained unbeaten in its group after defeating Romania on Maria Jose Martinez Sanchez's singles win and an injury retirement by Victor Hanescu.

Hewitt won the first three games of his match with Isner in eight minutes, and faced a break point while serving for the set before hitting two aces to win. He broke Isner's serve in the 11th game of the second set, then held serve for the win.

"I played extremely well," Hewitt said. "John's always going to be an awkward player for anyone. I played him a couple of months ago (and beat him) so I kind of knew what to expect."

Stosur lost in three sets in Australia's opening match to Romania's Sorana Cirstea.

"It's a lot better walking off the court a winner than a loser," Stosur said. "I thought I played pretty well today."

Stosur won the first set in 26 minutes but faced a tougher test in the second, saving three break points before securing a break of her own to open a 4-2 lead. She converted three of seven breakpoint opportunities and had 14 aces.

SI Apps
We've Got Apps Too
Get expert analysis, unrivaled access, and the award-winning storytelling only SI can provide - from Peter King, Tom Verducci, Lee Jenkins, Seth Davis, and more - delivered straight to you, along with up-to-the-minute news and live scores.