Kerron Stewart wins the second semi final of the women's 100m (© Getty Images)
So now we know. It is be the Jamaicans who are likely to pose the strongest threat in the final later tonight.
After the early sparring in yesterday's heats and quarter finals the race to find the 'world's fastest women' stepped up a notch in front of yet another full house at the Bird's Nest Stadium.
In the first semi-final we expected the main action to come from the four middle lanes, which was split by two Jamaicans and two Americans, and so it proved.
After a long hold it was 21-year-old Jamaican Shelly-Ann Fraser who established a clear lead by 30m and she maintained her advantage to cross the line in an impressive 11.00.
Behind her, US champion Muna Lee produced a solid 11.06 for second with Commonwealth champion Sherone Simpson of Jamaica 0.04 further back in third.
The 2005 World champion Lauryn Williams of the USA, however, looked a little ragged in qualifying in the fourth and final qualifying position.
Williams, who won the 2004 Olympic silver, crossed the line in 11.11 but will need to show much more if she is to feature in the medals in the final.
Behind them 36-year-old Bahamian Chandra Sturrup's bid to make her third Olympic 100m final - she also appeared at the 1996 and 2000 Games - ended in disappointment as she wound up fifth in 11.22.
In the second semi-final world No.2 Kerron Stewart produced a tidy, relaxed piece of sprinting to take heat two in 11.05.
While not quite 'Boltesque' in its dominance she recovered from a slightly lethargic start to power through over the last 30m and signal her ambition for the final.
Stewart, who was so relaxed when she was announced to the crowd before the race she appeared to be grinning, will probably start a marginal favourite later tonight.
Torri Edwards, of the USA, had looked impressive in yesterday's quarter finals but struggled to rediscover the same fluency and had to settle for second in 11.18.
A further 0.01 back in third was World Indoor 60m silver medallist Jeanette Kwakye. The 25-year-old benefited from a blistering start to become the first British athlete to reach an Olympic women's 100m final in 24 years.
Debbie Ferguson-McKenzie of the Bahamas bagged fourth in 11.22 to qualify for her third successive Olympic 100m final.
There is no place in the final eight, however, for defending Olympic champion Yuliya Nesterenko of Belarus, who had to settle for fifth in 11.26. European champion Kim Gevaert will also play no further part in the 100m. The Belgian was sixth in 11.30.
Steve Landells for the IAAF
