Updated

Misty May-Treanor and Kerri Walsh of the United States began their gold medal defense in women's beach volleyball with a win on the first day of group play at the London Olympics.

May-Treanor and Walsh, who have won gold at the last two Summer Games, posted a straight-sets victory over the Australian duo of Natalie Cook and Tamsin Hinchley. The Americans won the opening set, 21-18, and took the second by a 21-19 score.

The Chinese team of Zhang Xi and Xue Chen, who won bronze in Beijing, were handed an upset in their opening match of the tournament, losing in three sets to the Russian duo of Anastasia Vasina and Anna Vozakova.

On the men's side, the U.S. team of Jake Gibb and Sean Rosenthal posted an easy two-set victory over South Africans Freedom Chiya and Grant Goldschmidt.

Group play continues for both men and women on Sunday at Horse Guards Parade.