Usain Bolt's bid for an unprecedented Olympic sprint double double in the 200m is the highlight of the seventh day of athletics action at the London Games.
Bolt arrived in London saying he wanted to to establish himself as a "legend" of track and field by becoming the first man to win the 100m and 200m at successive Games.
He won the 100m and 200m titles at the Beijing Games in 2008 and won the 100m in London on Sunday. He is now just 20 seconds away from the double.
Bolt, 25, finished his 200m semifinal in 20.18s on Wednesday after slowing in the closing stages at the Olympic Stadium.
Yohan Blake from Jamaica and Wallace Spearmon from the United States also progressed to Thursday's final.
The 200m has always been Bolt's favourite event, but the world record holder will have stiff competition from Blake, who beat Bolt in the Jamaican trials and ran the second fastest time in history last year, Reuters reports.
Although Bolt's air of invincibility was dented by that defeat, he comfortably won the 100m gold in London - and anything but gold again would be an upset.