Serena Williams returns in her match at the Hopman Cup Thursday

The U.S. team of Serena Williams and Mardy Fish beat host Australia, 3-0. Williams beat Alicia Molik in women's singles, 6-2, 7-6.

Fish downed Peter Luczak in two tiebreakers, 7-6, 7-6. The Americans won the mixed doubles, 6-2, 6-3. The U.S. team ended round-robin play undefeated, the only team without a loss in Group-B.

In Group-A, Serbia defeated Argentina, 2-1, when Novak Djokovic teamed with Jelena Jankovic to win the doubles in three sets over Gisela Dulko and Juan Ignacio Chela (6-1, 3-6, 7-6).

Earlier, Jankovic pulled out of her singles match with Dulko because of a lower back strain that also forced her off the courts Wednesday. Djokovic won his singles match over Chela in straight sets, 6-2, 6-3. The Serbians also ended round-robin play without a loss.

Friday's final will be the ninth U.S. appearance in the 20-year history of the tournament. The Americans are trying to win the event for the fifth time.

Some information for this report was provided by AFP, AP and Reuters.