Jamaican sprinter Usain Bolt has turned his attention to winning a third gold medal at the 2012 London Olympics.

Bolt will likely be rested as the men's 4×100 relay team takes part in the preliminary round, but he says he will be on the track for Saturday's gold medal race, in which the Jamaicans are favored to defend their 2008 title.

A win in the 4×100 relay will give Bolt an unheard-of Olympic “triple-double,” following his repeat wins in the 100- and 200-meter events.

Friday's gold medal event in the women's 4×100 relay includes U.S. and Jamaican squads that are seeking to atone for their failures to win medals at the 2008 Beijing Games.

Meanwhile, Ethiopian long-distance runner Tirunesh Dibaba is seeking her own Olympic “double-double” when she defends her crown in the finals of the women's 5,000-meter event. Dibaba won the 10,000-meter race last week, repeating her triumph from the 2008 Games.

Also, the star-studded U.S. men's basketball team will meet a veteran Argentina squad for a chance to play for another Olympic gold medal.

The first gold medals Friday came in swimming and sailing.

Tunisia's Oussama Mellouli finished first in the men's 10-kilometer swimming marathon at London's Hyde Park. He thus became the first swimmer to win gold medals in the pool and open water, following his victory in the 1,500-meter freestyle at the 2008 Beijing Olympics.

Also, Australia won a gold medal in men's sailing and New Zealand did likewise in women's sailing.

In total medals, the U.S. and China remain far ahead, with Russia in third place and Britain in fourth. The U.S. and China are about even in gold medals.