Serena Williams shrugged off her jet lag to lead the United States to a 3-0 victory over the Czech Republic at the Hopman Cup mixed teams tennis tournament on Monday.

Litde more than 24 hours after stepping off a marathon flight to Perth, the seventh-ranked Williams opened her season with a three-set win over Lucie Safarova, and said she still had the desire to regain the top world ranking.

"Of course, I want to be number one and I want to win Grand Slams," said Williams, who has already won eight Grand Slam titles.

"I wouldn't be out there if 1 didn't have those goals.

Williams thrashed Safarova in the first set 6-0 thanks to her big serves and powerful ground strokes. But she lost her range in the second and the 23rd-ranked Safarova fought back, forcing a deciding third set.

The 26-year-old American's experience then came into play, and she showed her trademark grit to secure victory, 6-0,2-6,7-5.

The Group B tie was decided when an ailing Tomas Berdych was forced to withdraw from the mixed doubles against Williams and partner Mardy Fish, giving the United States an unbeatable 2-0 lead.

Fish was given a walkover in the men's singles, completing the 3-0 sweep.

The Americans are now in prime position to reach Friday's final, having beaten India in their opening tie on Saturday when Meghann Shaughnessy filled in for Williams, who delayed her arrival here due to illness.

Williams, who held the top ranking for 57 consecutive weeks in 2002-03, dropped to a career-low ranking of 140 in mid-2006 and started 2007 ranked 95th.

She began her climb back up the WTA rankings in January by claiming her third Australian Open title, thrashing Russia’s Maria Sharapova in the final.

Commentators have often-questioned Williams' commitment to the game, as acting, modelling and charity work have sometimes diverted her attention.

While she conceded she faced a tough task to dislodge Belgian ace Justine Henin at the top of the rankings, she said her determination should not be underestimated and was more confident in her game than 12 months ago.

"I love challenges and I do best when I'm faced with one," she told reporters.

"Last year I wasn't even in the top 60andnowl'minthetop 10."

Tennis legend Martina Navratilova watched Williams’ singles match and said she had never seen her in better physical condition.

In the third set, the 20-year-old Safarova was up a break leading 4-2 and had a game point on her own serve for a 5-2 lead.

But Williams broke back to 4-3 and broke again in the 11th game when Safarova pushed a forehand wide for 6-5, before serving the match out

Williams — who teamed with James Blake to win the Hopman Cup in 2003 — said she was disappointed with her form, but pleased to post a win.

"Lucie's a very good player --1 wasn't feeling really motivated and I felt like I wasn't moving at all," Williams said.

"I was able to pick up my game at the right time. She had a chance to go 5-2, and I was able to bring it through. That is really satisfying and very pleasing."