Jamaica's Usain Bolt reacts after competing in the men's 200m semi-finals
Usain Bolt moved to within one win of an unprecedented second successive Olympic sprint double here on Wednesday as he won his 200m semi-final in impressive fashion.
Bolt - who retained his 100 metres crown on Sunday - never had to move out of first gear in his semi-final as he won easily in 20.18sec ahead of young South African Anaso Jobodwana.
Victory for the 25-year-old Jamaican in Thursday's final would better the record of American legend Carl Lewis, who won three golds and a silver in the sprints at the 1984 and 1988 Games.
"The aim was all about just getting through," said Bolt, who has said he will only be happy being called a legend if he wins the 200m title for a second time.
"I wanted to run the corner so I really pushed myself in the first 70 metres and then I tried to take it easier."
He said there was "no doubt whatsoever" that he would successfully defend the crown he won in Beijing four years ago.
"People always doubt the champion but I know what I can do so I never doubt myself. This is my favourite event so I am looking forward to it."
Bolt said the final could well see his world record of 19.19sec tumble.
"It's a possibility, definitely. I can't say but the track is fast, it's going to be a good race."
His main danger will come from compatriot and training partner Yohan Blake, who took silver in the 100 metres, as the man nicknamed "the Beast" also won his semi-final with ease.
Blake eased up long before the line having done the hard work on the bend to time 20.01sec, the fastest time of the three semis.
The 22-year-old Jamaican insisted he could deny Bolt the title, the one the champion considers his favourite event, and that it may require a world record to do so.
"I think I gave away the 100 because I tied up a bit but I think in the 200m anything is possible," said the 22-year-old.
American veteran Wallace Spearmon, who was disqualified from bronze four years ago for treading in another lane, held off the charge of France's world bronze medalist Christophe Lemaitre to take the second automatic qualifying spot.
Lemaitre, European champion in the event in 2010, reached the final as one of the two fastest losers.
Lemaitre's successor as European champion, Churandy Martina of the Netherlands, won the third semi-final and could be a dark horse for a medal.
Like Spearmon, Martina will be looking for redemption as he was disqualified from second place in the Beijing final for a similar offence.