The United States booked their place in the Hopman Cup final by moving into an unassailable 2-0 lead over Australia in their Group B match in Perth on Thursday.

Former world number one Serena Williams [Images] beat Alicia Molik [Images] 6-2, 7-6 to put the number two seeds ahead and Mardy Fish [Images] edged out Peter Luczak 7-6, 7-6 to seal victory.

"I served really well today," Williams told reporters. "Alicia has one of the best serves in women's tennis but I think I returned well and everything is coming together well."

Williams, who did not concede a single break point in the whole match, ripped through the first set in less than half an hour.

Australian Molik, who reached a career-high ranking of eighth in 2005 before an inner-ear infection put her out for six months, saved break points in the ninth and 11th games to force a tiebreak in the second set.

Molik then saved two match points at 6-5 and 7-6 but a double fault gave Williams victory at the third time of asking.

In the other Group B match, the Czech Republic gave themselves a first win of the week as they took an unassailable 2-0 lead over India.

World number 23 Lucie Safarova held off the challenge of Sania Mirza [Images] to put the Czechs ahead with a 6-2, 4-6, 6-3 victory.

Tomas Berdych, who, like his girlfriend Safarova, struggled with a virus early in the week, then beat Rohan Bopanna 6-4, 6-0.

Later on Thursday, top seeds Serbia can seal their place in the final by beating Argentina. France [Images] play Taiwan in the other Group A match.

• Complete tennis coverage
• All you want to know about Sania Mirza